Unfortunately you are 6 months too late for Matter nightclub on the o2 site
No idea where will be suitable for you
Bit short notice too
London radio stations with probably a suitable audience:
http://www.capitalfm.com
http://www.bbc.co.uk/radio1 - covers whole country but mainly based in london studios
http://www.totalkiss.com
http://www.xfm.co.uk
There's probably more but I can't think of any at the moment