Well close to me there are both Broomhills shooting groundin Markyate (near, Dunstable) and the A1 shooting groundat South Mimms Services (well, 2 minutes down road). Both are CPSA registered I think, plus they have good sporting layouts to competition standard.
Alternatively, maybe we should do a quick count up and see how many people are interested, then plan something halfway 'ish' from everybody. Plent of grounds around for that to be practical.
Peeersonally, I'd prefer to make a good day out of it, nice BBQ, few drinks (after the bang bangs are safely stored away) and do it in a field somewhere. I have a pallet load of standard and midi clays, all we need are some traps and a willing land owner