From memory the RAOC have a big barracks at Bicester
Bicester, is an expanding market town which retains some interesting buildings, including the Market Square, with 16th century buildings around it, and St Edburg's Parish Church.
As well as shops, there is a sports centre and swimming pool. You can shop to you drop at Bicester Shopping Village, just south of the town.
http://www.oxtowns.co.uk/bicester/
Sounds pretty good