I'm based in East London. Used to go TWA Urban and haven't been to TWA Woodland for a very long time. Been plenty of times in the past to Bunker 51 but that site frustrates the hell out of me. Billericay is a good site and so is Dragons Lair in Brentwood which is easily accessible. If your doing the zipcar we could arrange to split costs as getting to some of these sites by mainline trains is cutting timings fine at times, especially if it's a Sunday. There are more of us on AFUK who are London based and I have a small Facebook group for London based skirmishers.