Hi there Pawel.
If you are looking for a London BSAC club, try Clidive (
Clidive, award winning London scuba diving club ).
Meet on Thursdays at Ironmonger Row Baths ( Near Old Street ) for pool night ( and a couple of shandies after ).
There is a very active dive programme ( diving all round the UK plus red sea & France for warm water this year - see website ) and lots of training as well ( including boathandling to learn to drive one of our 2 RIBs ).
I have stayed a member even though I have moved to Bournemouth as they are a good bunch and the diving is excellent. Give me a shout if you want any more info.