After playing airsoft for over a decade, I've seen my fair share of sites and games. Here's a bunch I'd reccomend for y'all. FYI these are mainly Southern UK based.
RIFT AIRSOFT
A fantastically run series of sites with lots of expirence putting on a good skirmish day. These guys I really recommend to new players as they provide what I would consider a perfect introduction to airsoft.
GUNMAN AIRSOFT
Another series of really well run sites by super expirenced dudes. If you're after something a bit more tactical than an average skirmish then give them a look in. Their universal and tiered ruleset gives them the opportunity to put on some cool historical games, with heaps of free clothing and equipment rental for the day.
ZED ADVENTURES - Z MART
Top tier CQB which scratches that itch for intense room breaching gameplay. The mid week night games generally have a nice tactical flow.