In reply to Ludo:
Ludo
As advised London is probably the worst place in the UK to go outdoor climbing , bouldering or else.
Personally would suggest to try a post of lifts and partners and head too the peak district ( 3hrs by car )or Dorset for the day ( 2hrs by car or by train)
As a Londoner Rock climbing always involves travel, good thing being either one of these venues will provide you with lots of good climbing .