Now for my favourite places to eat outside of Oxford (but close to it...). These are all a bit more expensive but very much worth it.
1) The Goose at Britwell Salome. Recently got its first michelin star (yay!) but happily, the price doesn't seem to have caught up yet. Tastefully decorated gastropub with spectacular food. Sunday is the cheapest day - a good roast, but not much you can do wrong with a roast really. Go on an evening to really get the best out of it. If you have the chance to try the lemon tart for dessert, do not pass it up - it is an almost orgasmic experience. Staff are really friendly and efficient, so no complaints at all.
2) The Old Butchers at Stow-on-the-Wold. Has been a favourite for a few years now and we first went when they were running the Kings Arms pub. Now they have a restaurant but the old regulars still pop in for a drink and a chat. Tasty, varied menu (it changes every day) with a good combination of fish and meat. Laid-back atmosphere - they really enjoy their food and they want you to too. Good on an evening but my favourite time to visit is on a Saturday lunch time for a long, unhurried lunch.
3) The Swan at Tetsworth. The chef used to run the Goose at Britwell Salome before it changed hands (and had a michelin star there himself). Now he runs the restaurant in the back of what is a rather large antiques centre. Eccentrically decorated but in a good way (for example, our table had been an old sewing machine table at one point) with very skillfully cooked food. Portions seem a little small initially, but you do come away full. The only fault would be that the menus don't seem to change that often so you can end up having the same meal twice. Afterwards, you can waddle around the antiques centre until you're ready to drive home...