Cirencester CC site is also excellent - especially for your staffie. If he head towards the top of the site there is a large dog walk which is fenced off so that dogs can be let loose without the worry of them getting lost. There are also ample doggy bins - 5 in total on the dog field! If you want to go further afield you can walk into Cirencester through the part, again great for our four legged friends.
If you wanted to go further north!!! There is Blackwall Plantation, Ashbourne, Derbyshire. The site is located beside one of the largest man-made reservoires in this country. Great walks again for dogs.