If you're going to Bristol you'll be going toward Somerset. It's a beautiful rural area. Depending on your budget, I recommend the Ston Easton Park hotel in Ston Easton, Somerset. It's pricey but worth it. 17th century country home in a pastoral setting. Great kitchen and personalized service. About 125 pounds/night as I recall.
Oh the countryside sound so wonderful- the train ride to Bristol is probably all we'll get to see of it, but I am really looking forward to it. And I'd love to do it next time! **taking notes**