Devon is located a few hours south of London and is easily accessible by train. However, I recommend that travelers make arrangements for transportation before arriving in Devon, as the locale is unabashedly rural. Many I've met in Devon make the long drive from London just to enjoy the scenery. (Yours truly is a train rat, quite frankly.)
I shall refrain from naming the bed and breakfast pictured below, and for exactly the opposite reason than one might suspect. The lodge is booked far into the future and takes no new customers (only repeats)! It is somewhat of a newcomer in the neighborhood, being built in 1714 and restored over the past decade. (My room is always on the second floor, overlooking the trout pond.)
Much of the rest of the village of Upottery, pictured below, was built in the 15th century. The village pub is usually jammed in the evening with wonderful and hospitable townsfolk (and the food is quite good too).
Of course, one can locate Devon bed and breakfasts on the Internet, but let me tell you how the Londoners do it. Most will leave the city in the early morning to arrive in Devon before noon. That allows for enough time to arrive at the post office of whichever town they may wish to explore. The postmaster can tell the travelers where the bed and breakfasts are (and occasionally make a referral regarding the travelers taste). Then the travelers can wander from one place to the next until they are satisfied sufficiently to settle down for the day, weekend, or however long they may stay. It adds an exploration ethos to the journey, which adds to the fun of the trip! There are more than enough bed and breakfasts in Devon to accomodate everyone, so if one lodge is full, just move on to the next.
I enjoy Devon for the historic architecture (not only Saxon and Norman, but pre-historic sites too). Most come for the sheer relaxation, others to enjoy the pastoral scenery. If you have visited London one too many times and want to get out of the bustling city, rent a car and discover a bed and breakfast in Devon. It's the most beautiful place in England.