As far as I'm aware the Welsh subsist entirely on a diet of lamb and leeks.
The Scottish have haggis, the contents of which is disgusting, if that sort of thing bothers you, but which is also delicious.
Irish food is broadly similar to British, I've found. Except they have white pudding on their fried breakfasts instead of black. Oh, and Guinness, which constitutes a meal in its own right.