We have also stayed at the Knoll House Hotel in Studland Bay, Dorset, and I really recommend them! I started going aged 8 with my parents and family, and we used to spend every Easter weekend there, because Mum and Dad got such a break too! They were pretty leading edge in terms of child friendliness 25 years ago, and still are in my opinion!
The children's meals (lunch and special high tea) are healthy and varied, the adult food good too (plenty of it!), and there is a wonderful adventure playground (enclosed) as well as the beach nearby. The bedrooms are perhaps on the old fashioned side, decor wise, but there's no danger of breaking fragile ornaments, and the baths are big enough for 3 children!
The baby listening works very well there, as they have lots of staff sat at regular intervals down the corridors. You can either give them the parent bit of your monitor (we labelled ours with our surname and room no.), or they simply listen out. In almost all cases I think they can actually hear the children crying from where they sit. On the rare occasion our daughter woke, we were informed immediately, and found she'd never been crying for more than 5 minutes, as someone rings through to reception to get you called from the restaurant.
The children's lunch is timed to be just before the adult one, and is followed by a supervised session in their indoor secure playroom (videos, colouring and toys), enabling you to go and have a peaceful adult lunch once you've helped them eat theirs. Our daughter actually napped during our lunch, and we simply took the monitor into the dining room with us, having requested a bedroom that was at that end of the hotel, to avoid too much interference.
Knoll House isn't the cheapest of UK hotels, but we think it's worth it in terms of getting the child bits just right.