Also see the Tolkein's Shire section of this page
And this one
http://www.bplphoto.co.uk/TolkiensBirmingham/TolkienSarehole.htm
It's likely though that JRR would have been inspired by a number of areas and it's also clear, to my mind, that he had a great love of the English countryside. The surroundings of Oxford would have certainly made an impact. He's been quoted as saying that one of his aims in writing the Great Work that he wanted to create a mythology for Britain.