A relabelled Dahon is the right answer. I bought it second-hand as an experiment but it has a few niggles (for example, the chain is a bit naked/unprotected/able-to-oil whatever it touches when folded and I think the hinges may corrode easily) - it works OK but I think hub gears make more sense.
As I was cycling home from market yesterday, I met a man from Nottingham who was riding a B'Twin folder to scout out cycle routes from the caravan site he was staying at, to check they had clearance for his wife's motorised wheelchair. I think he was on a
http://www.decathlon.co.uk/tilt-700-folding-bike-grey-id_8300175.html - the handlebar folding catch had come loose, but he said they were going to replace it under its lifetime warranty. Besides that, it looked much neater and better thought-out than my folder - but fortunately not as neat as the black roadster I was riding