Hi Adam- The best place to make that enquiry might be at a Yahoo group called Twintubemporium. Plenty of folks there from the UK who know where older machines and repair parts can be found. Also one never knows, someone might have a spare one you could buy.
There are also files containing reviews from Which? magazine, that are useful for getting some information on the relative strengths and weaknesses of different models. From my reading, it seems that manufacturers made frequent changes in response to review criticism; so from one year to the next might make a big difference in terms of an item that affects reliability or safety.
Check this out (see URL below). If the URL doesn't work, go to ebay.co.uk and put in item number 3879513777
Twenty-year-old Servis Supertwin, reconditioned, seller says in perfect working order. Item is in Lincolnshire, seller will arrange for local pickup only. I don't know if this is geographically near where you are, but anyway, there it is.