U.K supermarkets are huge and have a massive amount of products , like ASDA selling 19 different varieties of fresh tomatoes as well as numerous varieties of tinned tomatoes and tomato sauce and tomato paste and tomato ketchup.
Sometimes supermarkets do indeed sell out of produce , only takes a restaurant owner to go into a supermarket and buy all the onions , buy by the sackload and that's it , no more onions until the next truck delivery (which are daily)
But if you go into a supermarket and they haven't got what you want , then just buy a similar product or just buy something completely different .
Does it really matter what you have for dinner that night ?
Like, if they don't have carrots, just buy parsnips instead