My two pence on some mentioned:
I played Upwood once and it was great fun, it closed before I could return. That was a great site.
We were planning on going to the sandpit then heard it closed, I regret never getting to play there
Blitz in whitechapel, well I had forgotten about that. Had a bittersweet experience, the site was lovely just had a few too many players and the limited space meant every game despite the objectives were pretty similar but was fun. Would have been cool to try some private games there but again it closed shortly after we found out about it.
The Mall would HAVE to be the most missed site for me. I started playing airsoft there and loved it from day one. Yes there were days with issues with some idiots, but you get that at most sites. I never understood the bad reputation the mall had though. I played sundays, weekdays, special weekend games, private games, closed games you name it and still didnt see why it had this aura of being this magnet for cheats, 45 min brief etc. So many unfounded reviews and rumours about the place it was unreal it became a running joke with regulars and marshals.
I have had so many cool moments and seen some crazy things there I was gutted to hear it closed and even more gutted I was unable to play a game in its final days as they all sold out really quickly.