Hello. We have. Twice and it was absolutely great fun! The first time was Caythoroe hall and the second was Barton Hall. We enjoyed Caythorpe better - we were matched with other one child families and there were supervised activities for the kids in the evening. Barton hall was lovely too - there's a pool but no supervised activities. Definitely do it. It's such fun and quite a reasonably priced holiday. The food isn't great but that didn't bother us.
The accommodation is pretty basic to be honest. We were in shaker style rooms with bunk beds but there's shower / loo in the room. I brought a kettle and our cold box. The activities were fun and we had a great time so we didn't mind too much.