Depending on your tastes in music and men there are plenty of options to choose from in London. I would suggest looking up the online editions of gay scene weeklies such as BOYZ or QX. That should give you the info on what clubs to try out. The bars on Old Compton Street or the Prowler Store on Brewer Street will have flyers and promos for regular and one off nights.

I do have to say that the Royal Vauxhall Tavern is always great fun (though rather small). Duckies on a Saturday or the DE Experience on a Sunday have to be experienced to be believed ;-). I haven't set foot in Heaven since 1994 when I was a 20 year old University student. I didnt much like it then.

Oh and I am sure you have already been told this but to make use of the public transport system in London get a prepay Oyster card and don't buy paper tickets. It is much cheaper and easier to use the oysters. They are valid on the tube, buses, dlr, trams. So you can always hop the bus bat to Belgravia. http://www.tfl.gov.uk