Try an archive search, there is quite a lot on CP. There are about 4 in UK, more in Europe, UK ones are in Suffolk, Cumbria, Wiltshire (or is is Gloucestershire) and NOttinghamshire (I think). The whole point in a way is that they are great for kids, but I have had child free friends who went because of all the activities.
Well we recently hired a 3 bed villa (the accommodation is lovely) for £400 in June, for four nights. That was split between two couples. So for £200 we had a five day break, which included free entry to the swimming pool. We stayed in a beautiful place in the middle of a forest, self catered (cheapest way), and paid for a few "treats" - spa for me, some clay pigeons etc for him, golf for the other couple. We hired bikes, but you can take your own. Not sure if this is great value or not, but it seems ok to me. Biggest plus is that dd (3) was in her element - just so much to do.
hermione we recently been to centre parcs in longleat. it was amazing and fab for kids of all ages. we came home and bought a trailer for the kids that goes on the back of your bike. they all use them at centre parcs to get around. they are fab.