I don't think the folding bike range in the UK is much different from the USA. Very few high street cycle dealers stock folders and if they do they will be from major suppliers e.g. Dahon. Dealers often have contracts with suppliers and stock a limited range of most things including; Helmets, clothing, accessories and components. A large bike shop near me has many Specialized and Cannondale bikes with the odd Trek for variety - and that is about it as choice goes. Oh, and don't ask them about Campagnolo because there will be non in the shop.

I bought my Xootr Swift on-line (as I do most things these days) because only one shop in the UK stocked it and that was about 300 miles from where I live! The OP mentioned that the Swift does not fold as small as a Brompton etc but that does not matter to me. I don't need a bike that folds ultra small as I do not use it when hopping on and off public transport. The Swift slips nicely into the back of my small car and that allows me to drive to distant locations to ride new roads. High street businesses will only stock what they know they can sell which is why internet shopping is growing.