You have had an excellent suggestion from "Jon".
As regards where to stay, Swanage is good but rather out on a limb. Alternatives in Dorset include Wareham, Wool, Dorchester, and Weymouth.
Further attractions include Maiden Castle, just outside Dorchester, which is not a castle at all but something even more extraordinary, the Purbeck Way across the ridges of the Purbeck Hills, Kimmeridge (for its fossils), Studland Bay, Old Harry Rocks, Durlston Country Park just outside Swanage and, when the army open the range walks, the hauntingly sad deserted village of Tyneham, the neighbouring Flower's Barrow and what has been called the finest bay in England - Worbarrow Bay. There is also Lulworth Cove and Durdle Door.
Enjoy - you will return !