Frost Garden Centre - Surprising if you never went, but they have a really nice spacious coffee, where they provide coffees made with quality beans and expert baristas. They also have nice cakes and stuff. (Their lunch section is a bit disappointing for me though)
Restaurant:
Calcutta: in Stony Stratford, this is a really nice Indian restaurant, in a former church that just makes it such a breathtaking restaurant. The food is also really nice