I don't really know myself - I know three not too far from Westminster (can't remember exact addresses), but I'm not sure exactly what they have. I know there is Pleasuredrome, which I think does have a maze, Chariots in Waterloo (actually other side of Westminster Bridge from Waterloo station, by quite a distance I remember), and one called the Locker room, which is quite a bit further south, just off Kennington Road - I'm pretty sure I walked past Chariots while heading to Locker room when I was down (January), and I was in the Days Inn Waterloo, just on the junction between Lambeth Road and Kennington Road, about 5 minutes at a quick walk from Westminster Bridge. Locker room wasn't too bad, really. Others might be better. If you want to see if there's any closer to you, try Squirt - they have cruising listings, including saunas, cottages, public areas that are used for cruising and clubs/club nights. Hopefully you see this in time to be useful to you, and I hope it helps.