To add, have a look at aps like Too Good To Go (I might be imagining it but there might be one for grocery shops too), as I understand it they offer up food from restaurants that would have otherwise been binned for low prices (or even free? I'm not sure).

Also Approved Food sell food that is past it's best by date, but still good to eat, at much lower prices.

There are also places, I can't think of what they're called right now, but it's basically a communal grocery shop where you take what you need, and pay what you can. Maybe ask your local foodbank if they know of anything like that?

Lastly, when I was looking for an example of that last one, I found this page that might be helpful:
https://www.scope.org.uk/advice-and-support/food-no-money-food-banks/