I think you're right Al, quite a few American brand machines were either imported or built under licence before WWII. Looks like a 1930s model.

It could well be 240 volt, although when it was built the National Grid was in its infancy, and so the UK power supply was a mishmash of different voltages, frequencies and some supplies were DC - although if it was kept in use for long enough it would have been converted to to 240v 50 hz AC. I've had a couple of 50s Hoovers from the Bournemouth area that were built to run on 200 volts and subsequently modifed, and a 60s Hoover shampooer from Brighton that was made for 115 volts - not marked as modifed, so I was never brave enough to plug it in, even though it had a 13 amp plug on it!