I'm not too crazy about that idea. Fallout has always had the theme of what if you took 1950s America's idea of what the future would be like and if it was blown up. England wouldnt have that 1950s American feel.
I don't know why people get so hung up on that idea. Granted, I like the reto 1950's americana thing, but to me that's not the end all be all of the game. Look at the titles of the games ...
Fallout: A Post Nuclear Role Playing Game
Fallout 2: A Post Nuclear Role Playing Game
Fallout Tactics: A Post Nulcear Tactical Combat Game
... none of them have tacked on at the end "set in 1950's America". Sure, the franchise so far has stayed in america and kept the reto 1950's feel, but that doesn't mean that it absolutely has to stay that way. If Fallout moved to a different country you could just have an alternate point of view. That doesn't mean that what's happening in American suddenly becomes any different. If the game were set in Germany, for example, maybe the conflicts over resources before the Great War caused them to stick to their nazi ideals and so a Fallout in Germany has a 1950's reto sci-fi twist based on how nazi's would see the future. If Fallout were moved to Japan, then perhaps instead of Mr. Handy robot butlers and the Brotherhood of Steel, we'd have Mr. Roboto worker drones and the Steel Samurai clans. You just alter the "reto sci-fi" view point to fit whatever country you move it too.
Being so ridged in sticking to 1950's Americana, to me, is like having bratwurst every single day for lunch. I like bratwurst, but after a while it gets old and I want a new flavor.