@Galaxi
Posted this on a previous thread but I'm on universal credits with young DC and started prepping a few months back. I started adding £2.50 per week worth of "prepping" stuff to my food shop, and have already got a solid supply.
Was basically something along the lines of
Week 1: Tinned fruit. 2 x tins of mandarin segments @ 35p each, 2 x tinned peaches @ 35p each, 1 x tinned pears @ 80p.
Week 2: Tinned veg. 3 x Tinned peas @ 20p each, 3 x Tinned carrots @ 20p each, 3 x Tinned sweet corn @ 35p each.
Week 3: pasta & rice. 1kg rice £1.50, 1kg value pasta 60p.
Without doing the full list, I have now got Tinned tuna, loads of beans, cereals, cereal bars, custard, jelly and value chocolate bars, water, long life milk and long life orange juice. Then toilet paper, bars of soap and toothpaste. I still have a lot more to get (going to do a few weeks of kids medicines/plasters etc) but literally £2.50 a week on this stuff goes so far and has done wonders for my peace of mind. If I never use it, I'll donate it to a food bank. No harm done.