The French Affaire in Stony has some great lunch / brunch options. Ole Tapas Bar in Wolverton is great. Most of the big food selling pubs will have options, but a special mention to The Navigation in Cosgrove who have GF options for all their Sunday roasts. I don’t think there are any gluten free bakeries in MK ( please somebody correct me if I’m wrong), but all of the big supermarkets carry Scharr and other GF products as well as their own lines. My wife particularly likes Marks & Spencer’s Made Without seeded bread.