There are a few deficiencies in Oxford's culinary scene.
1) We've eaten in maybe ten different Chinese restaurants in Oxford, but none of them really stand out. We've had particular problems finding good yum cha. Admittedly we were a little spoilt for this in Sydney, which has excellent Cantonese food.
2) More surprisingly, we haven't been able to find half-way decent fish and chips. Sometimes - even in places calling themselves "Posh Fish" - the fish has been pre-battered and is warmed up when you order it. Sometimes the fish is freshly battered and fried, but the result is chunky and unpleasantly oily. In the worst case the result is uneatable; at best it's ok. Sydney fish and chip shops are just vastly better - the worst fish and chips you'd get there would be much like the best you'd get here.
3) There don't appear to be any Vietnamese restaurants in Oxford and no cheap Japanese (there is one popular Japanese restaurant we haven't tried yet). Fortunately there are quite a few Thai restaurants, some of them reasonably priced.
4) It is possible to find decent coffee, but it's not as easy as in Sydney. And there are few Australian-style cafes (our neighbour Alastair, who visits Australia regularly, particularly misses these). Instead there seem to be a lot of specialist sandwich shops.