I toook DS1 (then aged 10) and DS2 (then aged 6) to Barton Hall in Devon for a PGL holiday a couple of years ago. Had a great time, and they still talk about it now.
Accommodation was basic - we had the one room with bunk beds and 2 single beds, plus en-suite. No "luxuries" such as TV. but there was a kettle.
We were there for 7 days, and food was generally ok, and quite a lot of it (but we needed it as we were burning up so much energy). First evening meal was not good, but after that it was fine - good selection, fruit always available etc.
Activities all great fun - we certainly didn't feel we were trapped in a nightmare of over-achieving /super-fit families. We were in groups of 12, stayed in the same group all week, so always did activities together. Grouped (I think) by children's age - we had 3 6yr olds in our group. All bonded well and by the end knew quite a lot about each other.
We did: basketball on a trampoline (v v funny), climbing down a wall (has special term but can't remember it), low ropes, orienteering, climbing wall, trampolining, archery, zip slide, survival, mountain biking and various others.
Activities also in the evenings, eg treasure hunt, talent shows, quizzes etc.
The weather helped, of course. The summer of 2007, when we went, was a paticularly rainy one. However the week we went was fantastic, sunshine every day. Am not sure if it would have been such fun if it had rained....
Have to add that this was not our "main" holiday. It is not a "get away from it all" holiday, and you are busy the whole time. I booked this on a whim in July - had been offered some extra work (a lot) in school time, so decided to treat DCs to this holiday. Booked it late, so prices had gone down quite a lot.
We all want to go back, taking DH with us next time!