I've have not had any success in London, in fact it was quite unpleasant, but it was several years ago and I was young and stupid (as opposed to old and stupid now). I was in Soho and went in a kind of bar that advertised a show and a cheap entrance fee (a couple of pounds). Once in, there was absolutely nothing happening, nothing. A waitress came to serve me a drink and I had something very tame, like a juice or a soda. In any case, after a while of nothing happening, I asked for the bill so I could leave. The bill was unbelievably outrageous, like 75 pounds (Can$150). When I inquired about this, it was explained to me that it was the price for the privilege to be in this special meeting club. Well, obviously it was a scam. To make a long story short, there was a lot of arguments, with physical threats from them and counterthreats from me to call the police. Eventually I gave them something like ten pounds and left while being insulted by all the staff that had suddenly appeared from nowhere. No a fun experience.
So, essentially, I did not understand the kind of action going on in the city, and as a total green horned tourist, I fell into a con game.
So, my word of advice is: be careful of scams, and try to get a good understanding of the hobbying scene from someone who really knows how things work over there. The whole red light district was actually pretty seedy and depressing.