Surrey hills was a good pace, although I was in the slow group, njee20's defintion of a slow ride might possibly have been a bit quick!
We just rode at the pace of the slowest rider, and stopped a fair bit, I think we did more than you guys, but I doubt it was any quicker really.
This was the GPS track for our group on the Surrey ride, with an overall average of 10.6mph, but that includes the road riding to/from my house, and I did some extra off road stuff on the way up, so I'd guess around 7mph or so for the group ride. I just aimed to do it all at a comfortable pace, keep racing for when you've got a number board on!
Definitely agree on the risk that the slow ones never get a breather, having been that slow one on a weekend in Afan it was very depressing to see the other guys chatting and recovering, only to ride off the second I arrived, refreshed, while I continued to plod! There was 3 hours of stopped time on that track, so that seems like a fair bit!