OTE is great - about £50 for entrance and a box of paint. Semi only with a 10 ish BPS limit and 280 FPS. If its a low turn out of walkons you'll mix with the renters for play and be expected to keep your trigger finger under control so as to not intimidate them too much.
OTE is definitely a good site to play. Have played it quite a few times and never had a a bad day. Staff are really friendly and always ready to help. Real mixture of walkons and rental players. Good brew shop as well. (Just make a donation and they'll keep you supplied all day)