Bricket Wood hosts the Southern Paintball League, with 6 events this year. Two divisions (mercy 2 and 5man) with around 8 teams each round. It's the main series for some teams who can't make it to CPPS, others such as Cardinals and Thunderducks use it as training for CPPS.
There are a few less teams this year though, after a some team breakups or progression to CPPS. Plus as Shoaibaktar states the cost of playing in two tournaments adds up pretty quickly, or real life hits.
BW also host a "fight club" training/scrim day for Elite/D1 teams before each CPPS.
One41 was hosting a tournament at their old site, will have to see what happens with the new location.