Well, I think the most of us owns one.....but may be not from the UK, so the running cost change from country to country..not sure about electricity cost there.
Dryers choiche:

For personal experience I can say european models generally changes like night to day from  american ones...  simply incomparable... european are kinda "toys"...

Over here in Italy because of high cost of electricity (the hghest of europe)  dryers are not that common, but gas models sold from speacial dealers along with agitator washers  are spreading always more...the cost of these machines is prohibitive for the most though...
Are also sold british gas models now, that generally have lower costs, but they're still averagely about 700-800 euros vs. the 1200- 1800 or more of US machines..
So since you're in UK and gas models of White Knight are "cheap" over there, about 350£ I suggest you go for it if you have a  gas hook-up available... not sure about gas costs in UK but generally gas is cheaper than electricity...and they're usually faster.
I never watch energy labels....I think they're BS..... most dryers  rated A, A+  yes they have lower consumption of Kwh, but usually they takes longer than others rated B or C... so that the consumption they have at the end is the same or sometimes more.
Not to mention condenser models, they generally takes longer than vented ones.... drying is different, laundry does not come out well as if dried with a vented one, but of course good (and only)  choiche for those that can't vent  outside.
So if you've the possibility I suggest you a gas model, or if not possible a vented dryer... Vintage, even better.
Leave alone newer stuff...
www.thegascompany.ie/iopen24/tumb...
www.applianceconsultants.co.uk/wh...

Even cheaper: www.greenandeasy.co.uk/white-knig...

Vintage....here is one, sturdy Philips: http://www.ebay.co.uk/itm/philips-d162-t...

A nice US whirlpool,dryer: http://www.ebay.co.uk/itm/dryer-/1511173...

Another whirlpool: http://www.ebay.co.uk/itm/WHIRPOOL-GOLD-...

Hotpoint: http://www.ebay.co.uk/itm/Hotpoint-Aquar...

Hoover: http://www.ebay.co.uk/itm/Hoover-Tumble-...

VGC Huebsch/Speed Queen: http://www.ebay.co.uk/itm/HEUBSCH-COMMER...

Credas: http://www.ebay.co.uk/itm/retro-tumble-d...

Hotpoint liberator, this is what you wanted?: http://www.ebay.co.uk/itm/HOTPOINT-17460...

Hard wiring a dryer.....well, there're a few school of thought about it, in the USA things changes than europe and UK and you actually are  generally *never* required to hard wire a dryer to a 240 volt hook up, they're generally already predisposed for dryers or stoves and so  wires are already large enough, so the same way plugs and oulets are  meant to  support it...
Hard wiring  it's  always recomended  in europe even if not *always* needed, this also and mosyly because some houses may have  too small wires  going to a plug,  especially old homes, so  hard wiring   is reccomended also to make sure the wires are big enough...
but  as said   this is not *always* necessary as long as you use a good plug and you're sure wires can support such absorbition...even  slightly  underrated household  plugs may be fine   but hey have to be good ones....otherwise you can opt to have installed a 220/240 volt industrial outlet..
dolnoslaskie.all.biz/it/prese-e-s...

I have seen a bunch of these dryers hooked up with simple schucko plugs over here in Italy, and as far as I know they worked fine... in one case  I also seen one  adapted to normal italian outlets ( the large pins outlets) with adaptors from 240 volt household hook-up to industrial one: www.bsmacchine.it/product_info.ph...<<

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www.shopmania.it/componenti-elett...

That was a church community near here that had it for the youth dorm/summer camp self  service laundry... I find italian plugs to be better than european standard schucko, they allows more absorbiton..
Anyway....
Now, since UK plugs do have an internal built-in fuse in the plugs,  if fuse is old or very delicate may easily blown with a 5000 absorbition, you'd have to change  it to a 18- 20 A one at least to ensure it will last the wattage (4800 watt) it will never blown for the 200-300 watts more...  but likely a delicate 13 A would blown..
Uk plug fins are well more large and could support the absorbiton way more easily... this differently than europe where some bad shucko can actually over-heat and melt.... but in case of UK is more a matter of plug built-in fuse and house wirings than plug itself..
Of course is advisable to hard wire... you'll have to verify it yourself if it's the case or not...

Yes...... of course...that's why I said  it as well  if you read carefully, is not a matter of plugs mosltly, but  rather of their fuses and of course house wiring...
This statement is clear:
"but in case of UK is more a matter of plug built-in fuse and house wiring than plug itself.".....

You better ask to an electrician,  especially if you're not particularly inclined about electric .....this is worldwide, not UK only..same thing would be for "our wiring" as you call it..if your circuit can't stand such absorbition you simply can't connect a 5000 watt dryer and ask for  it to work properly (and some circuits you find over here absolutely could not support it as they have too thinny wires)...not to mention if in your crcuit you've already connected a dishwasher or oven without having the slighest idea of it,  this would result in catastrophe if  the circuit safe fuse if present would not work as it should... BTW, over here generally there're not separate  fuses for each circuits like elsewhere...so it's really dangerous...
Mine was not to be meant as an advice,  just to clear things up...never gave one, just said facts..
If you would hook up a  5000 watts dryer to your regular outlet in UK you'd likely get your UK  plug  fuse blown firts and in the likely case your wiring isn't already much appropriated so underrated for the circuit that is ( example: wiring rated 2000-2200 watts used for 3000 watt circuits, thing  that over here I've heard was usual in homes built "looking at saving", like in our attic in the condo in front of the street, thing that  our electrician said  in 60s and 70s they all did in Italy)  you could get serious damages on your electric plant, and a fire hazard.... at best you'd need to change your circuit fuse if you have one, or re-do the circuit inside the walls....at worse you'd get a fire...
So better point it out ... you need to be careful on what you do, you need to know what you do...as for everything...

Allen, sorry, I'm not sure I can get the sense of the your statement about Netherlands.....

Anyway, for the "question" about heavy duty outlets in UK..... I think he started from the premise that one was not available.
In the USA  you can find a heavy duty outlets in kitchen (stoves) and in laundry spaces,  or areas that once were used as..
From what I know "heavy duty" outlets in the UK are usually found in kitchens only just for the stove or large appliances, most of the times stoves are hard wired with a special switch just for them next to ktchen service outlet/s serviced with special  high wattage wirings....  but I think that you could easily make  a heavy duty outlet wiring without many troubles and expenses...industrial plug or heavy duty for cookers that is can be also used..you could even buy a US heavy duty one and install it.

www.pennylaneelectrical.co.uk/cli...

The seller also started from the premise that a heavy duty outler was not available (not common in UK) so he just mentioned hard wiring as they do for stoves....

I'm not used with ring wiring system either... my understanding is that if you let pass two large L and N wires  separately connected to the the main source/wires where ring system  is connected to (30 amp??)  through the holes already existent for the ring system  you could create a heavy duty outlet near another normal already existent and just connect the ground to  the wire servicing  all the others "ring system" regular outlets...
You could do this also on the other side of the wall in the outside (patio, porch), but you'd need a little carpentry job...or at least a little drill  hole to let pass the wires and then make a heavy duty outlet screwed to the external wall...

All this if  the ring system tunnel/hole in walls is big enough to have those two large L &N big wires inside also...

I think  would be very useful to have a heavy duty outlet outside anyways...if someday you want to make a wash in outside at least you can have two machines heating at same time, not deciding turns for the one that has to heat the water first! LOL Jokes a part.... in the summer you could hook up lots of things and run a big party there...without having the risk the power fail for that outlet...would be nice..no??
Maybe I make the technical thing of making a new heavy duty outlet too simple.....but I'm not an electrician, not british and used with ring systems so can't really tell... I just guess..and wonder...

Voltage differences...
I remember these things from a documentary I watched time ago, not sure if I remember it correctly but that's what I remember:

In the USA it was a choice to deliver lower voltage for household use and  illumination (initially) and it was  made to solve the problem of people  dying elettroshocked due to bad wires  insulations of the early times of electricity  both external and internal ones....so it was a safety choiche, lower voltage meant less hazardousness
While in Europe for some reasons they  didn't care much of elettroshocked  people and they went ahead with higher voltage...
Then I also remember a few things about a stance taken by Tesla if I remember right and Edison about what voltage was the better...so for personal pride they just kept their own ideas and so different voltage in the two continents even if i a standardization would have brought considerable advantages....  substantially Edison said FY to Tesla and Tesla the same to Edison...
So things went ahead and they  never decided to standardize the things for the two countries....then later of course it was too late to fix things up...
I'm sure both the voltages have their own postives and negatives aspects respectively....so personally I can't really tell what I prefer of the two....

Honestly for the use for bed sheets and towels you're going to use it for, i think pretty much any dryer would work fine...but if you happen to find a very good deal  you should take advantage of it immedately!
Used is your best deal...not to mention would be a pity to have a new machine let in an outside  space to rust because of wet winter weather...if you buy a used one for a trifle you can even don't care much if it is going to die faster...BTW this is another aspect to consider...try too look for electromechanical timers/programmers ( better, stronger, long-life and more resistant to weather conditions)  and simple switches and controls  rather than newer junky  electronic ones that are more sensible, so to to fog  and humidity also...not to mention LCD stuff etc...simple and strong machines are better in your case...no too fancy electronic stuff that may suffer outside conditions...
 If I were in your situation I'd probably be more confused than before with all these different suggestions... but that's normal, everyone is different and have different tastes....
But for the use you have to make of it about every one would be good, as long as they're not chinese garbage like my last electric dryer named Bomann that I still have in the garage, and that I'm too honest to trim to someone...
It is simply unusable..... lint filter does not work, it is filmsey, it makes a terrible noise and had well 8 repairs (under warranty) in the 3 months I had it...
 I'd personally go for VTG 60s, 70s and 80s... but if you want a new one I say:
Stay away from Bomann and  newer  "crashed square door" Whirlpool models (the tangler dryers)....  the 6th sense style door for istance..
White knight is reliable...the cons about white knight that I could experience was a high level of noise (  inferior panel and control panel and door vibrations against cabinet) and fact that lint tended to get stuck in the door ring thus littering all around during emptying (not a big issue for outside though)..., then it had a too  small door access...
You may want one with a large door as to facilitate loading and avoid items dropped or rubbed on the outside dirty floor during loading and emptying opeation especially in the dark or in : "it's too damn cold out here, better hurry up and gets things done faster thus not caring much of what you're doing,  while you're shaking  like  Miley Cyrus  in the last MTV awards" situations ..I guess that would be better anyway...

Speaking objectively, euro dryers are better to have the reverse tumble as they have  way smaller  drum room compared to the size they're supposed to handle, this  compared to american dryers and rated size  that they're supposed to handle,  euro ones   do and would tangle and crease stuff alot more compared to american ones, reverse action is true prevent more tangling and creasing but does not solve or avoid it, it became a must for euro ones given the reasons before, true fact is that most american dryers do not have reverse tumble, but there is not that much of a need for them  like  it is indeed for euro models... on the other hand they have drums more than 2 times bigger  than euro ones  and tangling is possible but not so likely to happen..
I've seen  and owned euro reverse action dryers tangling items so badly that made and kept  balls of sheets bouncing  till the end cycle having them still wet internally and creased alot.... my whirlpool was a master doing that all the times and when I say all the times I mean all the times! I always had to be at home while drying them, so  interrupt the cycle, take sheets out unwrap them and resume... the typical BUM BUM BUM BUM  was the signal that it was time to do that...the   Bomann, Siltal and the  Zoppas (Zanussi)  we owned in the past   6-7  on 10  times would  have done that while drying large items too.... and you imperatively  had  to divide bed sheets and rest of laundry in two portions to do not have stuff  like if came out from  the  butt-hole of a chicken...
Since I own the  Speed Queen (no-reverse) tangling is happened just once.....and I never experienced it happening so often with other american dryers, like it was for euro ones I have used in my life...
US models have larger rooms, way more space to move the laundry, so tangling is not that common and creasing is almost unexistent...

But again for the use you're gonna do a euro-model would be more than needed...
Keep in mind, this is a personal advice:
If you're like most people that start with   your idea: "oh yes I'm going to use it just for towels and heavy hard to indoor dry stuff" be aware that the conveniency of a dryer is addictive..LOL   Jokes apart is of course a great convenience...who didn't have one can't really speak and cannot know!
I know many like you that  said that and then finished to use almost exclusively the dryer...you know: " I'm in a hurry, still have to clean house, stll have to go shopping, etc------ I'm gonna put this load in the dryer  this time, no time to hang it"...finishing then to do that almost always .. absolutely nothing wrong with it....it's more than normal...why waisting time and efforts having to deal  with the drudgery of hanging laundry if you can conveniently load and start a dryer in a few seconds, also having your load dried quicker?
Of course there is people who would still use it as prefixed.....
Anyway....speaking too much...
My suggestion is to go for the used market...as Launderess said you can find really good deals that will give you a really long life ahead of them, and  for way less than the half of their market value as if new...

So I'd go for the used..... whatever you decide at the end wish you good luck..

I'm glad I was helpful....
Compact dryers are a good choiche for people that actually do not really  have space in homes so that is the only thing they can fit...

That said.. if you have  the possibility to fir a regular euro size that would be better...I think...I used to always dry bed sheets alone  in full size euro dryers...as the results otherwise would have been improposable (for my canons) because of tangling and creasing...
I never owned a  3kg white knight dryer nor seen one in person  but I assume that would be able handle a king size bed set without having  improposable results...   but even if not improposable I think the  results would not be that good....
 More than tangling (that is anyway likely to happen because of small room) I'd be concerned about  the typical euro dryers creasing and limited space to air the load properly, what I call:  a  typical euro dryer "tight" load, so this  if the dryer you're using have a further smaller drum like a 3kg one,  a  King size bed sheets load plus  pillow covers  would not come out nice ...and so taking longer to dry and giving creases, not not much for towels (that are harder to get creased) but for bed sheets and else...
Here is a video of how a load of sheets + pajama would do in a compact white knight...personally looks like  a big  twisted and  wrapped ball  tumbling, not drying as it should and hus getting lots of wrinkles, would be nice to know the exaxt load composition (king size? Single? Heavy pajama? Thin Pajama?), but this gives an idea:


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