The London Scene is not about huge venues, but about small, ghetto clubs in North and East London. You can go into Camden, or the Mile End on a Friday night, and be in a place with perhaps 100 other people, and listen to the sickest, freshest music ever.
We have a few iconic places, like Brixton Academy, or the Electric Ballroom which play indie/ scene music. But the grime/dubstep/DnB that you stumble across is the true London music scene, in tiny venues, where there are no pretensions about fame or money or whatever, where both the crowd and the artists are there for the love of the music only.