All of the following are
free to get in except Club Aquarium...
I've had successful nights at Shoreditch's The Hoxton Bar & Grill / aka
Hoxton Square Bar and Kitchen (despite the name, is a club).
There's also a pub/club (Electricity) around the corner from Hoxton Square which has in its basement an
80's style dancefloor with brightly lit colourful squares. It's always packed in the two floors of that place, good atmosphere, fit women, good for pick up.
Also worth checking out if you like a very small club, perhaps for the start of the night, is...
The Hoxton Pony
Have spent time at Trafik and bluu (both are really just bars; Trafik is open much later than bluu, also has a tiny dancefloor downstairs), but didn't find either good for pick-up.
The Aquarium aka Club Aquarium is the club nearest the Old Street tube station. Open til very very late. Had a really shit night there, so didn't go back. Only one fit women in entire place and she was out her tree (drugs?), it is dirty and dingy inside and the music was trance-techno p#sh. (I like well-crafted dance music, but not that idiotic pish they played that night.) My mates hit the swimming pool at 4am (it doesn't open until then, just to continue everyone's agony while they wait for it to open) but I left 1/2 hour b4 that as I just couldn't be arsed
with Club Aquarium anymore.