The Sci-fi store would be Forbidden Planet. It's a chain with stores all over the country, there's one in Coventry City Centre. It sells all sort of obscurce things, including rare comics (new editions of rare comics, not old comics) and action figures for any film/tv show you care to mention. It's a great shop and their flagship store in London must have some brilliant stuff in it.
As of about a month ago you can drink 24/7 in many places, not all, but many. IF you move around once or twice in an evening you'll be able to stay up and drink as much as you like.
As for cool stores, there's Forbidden Planet I just mention but there are also the flagship stores for many other companies, including a Virgin Megastores which is so huge they have an entire wall (walls in this place are BIG) dedicated to kung-fu films
If you haven't already been to them, don't miss the Science Museum and the Natural History Museum (my personla favourite
).
And @ efthimios. You put the plug in the basin and mix the hot and cold water in the sink. The single tap (combined hot and cold water) system is getting more and more common in Britain.