Im studying in Oxford right now. Tuition fees + college fees would be about 23,000 pounds per year depending on your course/college.
As for your living expenses, it would depend on the lifestyle you lead! It might be tempting to think expenses can be kept very low but there are a surprising number of social occasions which you'd feel very left out of if you did not attend and some of them can cost some money (e.g. a formal hall dinner would already be about £10)
For more information on oxford/Cambridge student life you might want to see
http://gurume.co.uk/en/blogs/26
Hope this helps