Central(ish) or North/North East London. What recommendations (or warnings) do people have for such a place?

Details: It will be a private party, not promoted or tickets or anything. There will be anywhere between 20 - 50 people (and as a result I'm assuming it will be a pub with room affair). However there needs to be a proper set up, PA etc for the band to play.

Any stories about such venues good or bad gratefully received, thanks.