We recently visited Helmsley Walled Garden in North Yorkshire. It's a five acre garden that once supplied the Duncombe Estate but was abandoned in the 1970's. It's since been restored and is well worth a visit. We strolled around for what seemed like hours finding all sorts of interesting nooks and crannies to enjoy. It was a lovely place to spend a warm, sunny afternoon.
The garden is overlooked by the ruins of Helmsley Castle in the grounds of Duncombe Park.
I enjoyed one of the nicest salads I've ever tasted in the Vine Restaurant (note grapes growing overhead!) The puds aren't bad either. Incidentally, the restaurant is completely vegetarian.
Helmsley is about 25 miles north of York and I can highly recommend a visit.