My suggestion for the venue would be the Devonshire Cat, on the corner of Eldon Street and Wellington Street. It's about 16 minutes from the main train station and 4 minutes from West Street tram stop. I've been there a few times before gigs at the Corporation and quite like it in there.
A little close to the Bristol Splunch, which this year is on 16th May. Could I suggest late June, as I understand there won't be a London meet in June.
21st of March would have been amazing for me (would be in Sheffield anyway for a gig at the Academy), though it's a bit short notice and no doubt most people have plans already.
Was only kidding re: pieing in the pub! I know that's not a splunch thing! I'm definitely going to try to make it though - just might need to hush my voice a bit
Best bet is to contact mike mr bump he will probably know the splunch running order then you can find an available date which makes people able to travel from all over