Dunno about big (Campaign is pretty big... biggest I've been to, but that ain't saying much ) but Sparklie has what must be one of the DARKEST woods fields... so easy to lose orientation amongst the trees if it wasn't for the roar of the M4 nearby...
Do you mean largest single field, or largest site with most number of fields?
Hey Mr Pink! I used to go to Holmbush too - remember the massive rhoddy field at the bottom? You used to need a compass to get to the other base
Went back there last year - still excellent fields, although the Rhoddy field has been cut in two and everything is a lot smaller. Very good woods though, just a shame about the site infernos and dodgy paint