Some good tips here already (look for another food bank/pantry/church in your area that could help, follow dumpster diving youtube channels for advice), you could also try some of these, or look for similar sites (I’ve only skimmed these, not vouching for the content):
https://www.thebrokebackpacker.com/dumster-diving-for-dummies
https://wheeliebinsolutions.co.uk/blogs/advice/a-guide-to-bin-diving
https://www.woodfordrecycling.co.uk/news/skip-diving-junk-hunting-and-freeganism-the-need-to-know/
But more importantly, please have a look at/chat to turn2us, you are almost certainly entitled to some benefits, they will help you figure out which you are entitled to, and there are then benefits advisers in almost every town who can help you through the process if you find it too daunting and/or difficult.
Solidarity.
Just to add, give Approved Food a look, they 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/