ES,
Hi, I'm currently at OATS and used to reside in sunny Nottingham and believe me you dont want to even consider commuting!
Several off my course live in London and do that commute and it is beginning to take its toll.
Its not compulsary to live "on campus" but I think you will find it a lot easier to live withing a reasonable distance.
Living costs vary depending on what/where/how you want to live, but if you want more info on the Oxford area mail me at
[email protected]
Good luck
TBL