I'd really love some advice.

I've decided to put on a Christmas gig/festival type-thing in London. I'm determined to do it on a Saturday (ideally 17 December) and want to do have acoustic acts from around 4, bands from around 7 and DJs from around 11:30 'til late.

The thing is I've never done anything like this before and would hugely appreciate advice on venues which might be feasible. I'm well aware venues are gonna be hard to find on a Saturday that close to Christmas (hence me looking now). Becuase I'm planning to put on about 15 acts, and have a few channels where I think I can build a bit of a buzz, I'm hopeful I'll be able to sell enough tickets to make a 100-150 capacity venue worthwhile.

Does anyone have any suggestions/advice on whom I should approach/what I should do?