Hi Jo-anne,
We visited Longleat for the first time last Spring, spent 5 nights there and already booked to go back again in May. As others have said the site is well maintained and only a few minutes walk from Longleat House,Pets Corner and the boats that go out to feed the sea lions and visit gorilla island. The Safari Park entrance is about 5 minutes drive away.
The Pitches were level, mostly hardstanding with t.v booster points. Re walking your dog, we no longer have any but plenty of people there had four legged companions with them and seemed to find plenty of space for them to exercise. There is a dog walk into woods from the side of the site but I couldn't say what space there is, not sure if it's limited in any way.
If there is not enough at Longleat to keep you occupied Bath is not far away, neither is the Cheddar Gorge, Wookey Hole or the Fleet Air Arm Museum.
We arrived on the Sunday and the park and attractions appeared very busy, much quieter during the week and outwith school holidays if you can manage to go then.
We would recommend both the site itself as well as the House, Safari Park and other attractions.
Have you had a look at the site description on the C.C website? there are some photographs there as well.
http://www.caravanclub.co.uk/Planning your trip/UK Trips/Site Search and Book/Club Sites/Site Detail.htm?csid=LONGLEAT
The site itself is easy to reach as long as you follow the C.C. directions and don't use a satnav for the last sections.
Robert