We go to pillaton hall farm near Cannock chase
Enclosed dog walk area and of course the chase is on the doorstep
------------- April Peak District Beech Croft Farm
May Peak District Duke of York
May Holland Delfse Hout
June Cotton Arms Nantwich
july/aug Cornwall Pentewan Sands
And quite a few local weekenders
Not sure how far it is from you but Nene country park ie Ferry Meadows site is fab, just outside Peterborough , my dog loved it, miles of flat paths and water t swim
We have to avoid sites where reviews mention ducks as our rescue spaniel would kill one if she got out of her collar. Also, check other threads for helpful advice on how to secure your dog on site: crate, fence, different gadgets to screw into the ground etc. And have a fall back - a previous dog was frightened of being inside the tent so she slept in the car, windows open & all that stuff. You can tick the "dog friendly" box on the map search. If you're a CCC member, most of their sites have a designated dog walk though they vary in size. I can highly recommend The Rickels east of Kings Lynn where there's a pétanque pitch (BYO boules) in a massive well-mown dog walk area & loads of beaches nearby, Thetford Forest too. It's a different holiday with a dog - much better!
We're at Clover Fields in the Peak District at the moment, lovely adult only site with enclosed dog walk where dogs can go off their lead. Site has a lovely café which delivers to your tent.
Area is beautiful for walking, Pavillion Gardens in Buxton is lovely, lots of dog friendly pubs in the area too.
------------- May/June - Spring Valley
Aug/Sept - Leekworth