I suppose I'm kind of biased. I'm a Londoner, so the London lifestyle/entertainment isn't such a big consideration for me, as I consider it the norm.
At the end of the day, though, you go to uni first and foremost to study instead of to have fun. Obviously you'll do both, but if you go to Oxford and get a good degree, you'll be sought after by every top London firm/chambers. Plenty of time for living it up in London, then.