Guys, there really is no need to stay in central London if you're on a budget. There are plenty of hotels a bit further out that are within walking distance of an underground station. I've often used Premier Inn @ Kew Gardens for example. Way cheaper than a central London hotel (unless you get a really good deal) and still dead easy to get into the centre.
I live 35miles away from London, 20mins to Central London by Hi-Speed train, 400 yard walk and I'm at the venue, simples.