I have done two stints living in Oxfordshire. The first time in Wantage, a nice little market town about 20 minutes by car south west of Oxford, in 2008/9 it was costing me about £750 PCM + bills for a large 2 bed, 2 bath modern flat overlooking a small river. The least attractive town in the shire Didcot (10-15 minutes by car), is far enough away to be out of sight but close enough to be incredibly useful it is essentially a commuter centre with all the trains to bristol, south wales and Oxfordshire passing through it, so you don't have to wait any longer than 20minutes for an express which will have you in paddington in 45 minutes or so.
Oh not to mention you are literally on the Ridgeway, beautiful riding albeit not the most challenging. For challenging, just head back to didcot and hop on the train in the other direction and find your self at afan etc in around an hour, or exmoor/dartmoor in not much longer.
Wantage has a waitrose and large Sainsburys as well as loads of other useful little shops (including two LBS)