Hey live there and am posting from sweet Elephant and Castle (that sucks).
But London is a large city, with many types. What I would recommend you to do, is first do all the tourist crap, and then do some more chilled things. Go into clubs. If you like dance, house, hard house, its the place to be. Also all other styles are findable. Here is my fav website: www.dontstayin.com
Sthing else to do is friday evening in the City, the business part of town. Go in a beer garden with friends, go drink a pint, it is really nice.
Also, in Hyde Park, you can go swim. I went this afternoon to take a dip. Water was dirty but who cares, did it :).
Watching the girls getting really pissed is fun.
Picadilly Circus on Saturday is cool, Lamborghinis, Ferraris, Porshes come and scratch out a little bit.
More and more and more.
PM me if interested.