I used to spend about £15 a week, but I tended to go every three/four weeks or so and stock up on bits inbetween. So I would do a big shop of £40 and then a few mini trips here and there.
Carrots
Potatoes
Onions
Frozen petit pois
Frozen green beans
Gravy granules
Veg stock
Chicken stock
Rice
Pasta
Passata
Mince
Pork Chops
Frozen chicken breasts
Frozen chips
Turkey dinosaurs (mmm)
Heinz beans
Cereal
Bread
Butter
Milk
Squash
Pepsi Max
Then whatever else I fancied for that particular time - usually some wine (for cooking..), maybe some crisps/snacks/chocolate.. anything really.
I spend more now I think, and I basically exist on frozen chicken breasts, frozen cod fillets, squash, lettuce, cucumber, new potatoes, rice, risotto rice, stock, gravy, swede, carrots, petit pois, broccoli, granola bars, jaffa cakes, pasta and green beans.