Go back to the 80s, and grab yourself a pack or 2 of Walkers Snaps, only 10p each @ Home bargains, which I found in the Bletchley store.
These are usually around 40-45p each, but at 10p, it's about the same price they were in 80s, and the Spicy Tomato taste from memory doesn't seem to have changed at all, so stock up while you can.
Other crisps deals in Home Bargains..
Golden Wonder (My Favourites) 6 x 25g Chesse & Onion packs 69p
Golden Wonder Chip Shop Curry 34.5g only 15p each
BTW Best before dates are at least November