I definitely suggest Brick Lane for the best Indian in London. Brick lane is sort of the center of the Indian community...it is lined with restaurants to pick from. Kind of a different atmosphere...you'll have people from each of the restaurants trying to 'barter' with you as you walk down the street. One may throw in free beers, others may give you free Naan...its up to you to barter for the best deal and pick the restaurant you like best. Certainly a cool experience in itself, and as far as I know the most authentic Indian you can find...and cheap!