Depends if you actually want to stay in London or if you’re just looking for an easy in/out. When I used to live in Brum, I’d stay in Rickmansworth, Chorleywood or somewhere on the tube. Then it’s an easy jump back onto the M40. Also, more people will be heading south back into London after the gig.
If you’re looking to stay actually in London, hotels in The City (the financial district) are generally good bets at weekends as they’re a bit quieter than those in the West / West End.