Get the app 'too good to go' you get a reduced price bag of food, it can be hit and miss with what you get but it's always worth more than you pay.
My local carvery does a couple of take away carveries everyday for a very reduced price.
Offal - it's cheap and good protein, you might not like the thought of it but chicken liver pate is simple to make.
Buy a pot of frozen chicken livers this will be about 60-70p, leave them to defrost, put in a frying pan with as much butter as you can spare (I like 50/50 liver to butter but that's not always possible on a budget) add a chopped onion and any herbs you have to hand, salt and pepper and if you have some brandy at the back of the cupboard slosh a bit in.
Cook until the livers have changed colour then use a blender to create something that looks, well like something out of a nappy.
Don't let that put you off, pour into a container, cool and then put in the fridge.
Pancakes / Yorkshire pudding are made with the same batter of plain flour, milk and an egg. You can make a stack of pancakes and have them for breakfast or you can stuff then with something savory, cheese, onion, cooked mince, veg from the freezer You bake them in the oven for about 20 mins so they are totally crispy.
You can also make fritters using the same batter and add things like tinned sweetcorn, have them as a side dish or as a main.
Things on toast, beans, cheese, bacon, eggs.
Have a look at the tins in your cupboard, I was making a chili the other day and instead of opening chopped tomatoes I opened a tomato and basil soup, so I added it to my mince and it was surprisingly nice.
I always cook more than one baked potato (live alone) and will use the extra to make gnocchi, just put the potato in a bowl (remove the skin) and add flour and knead until you get a sort of dough, take off small chunks and use a fork to make little wedges.
Drop them into boiling water to cook and serve with whatever you can make a sauce out of.
Home made scotch eggs for some reason feel more substantial than a couple of sausages and an egg.
Boil eggs and shell
Use either sausage meat or get some sausages and take the meat out - I tend todo this using Lincolnshire sausages but sausage meat is cheaper.
I use 2 sausages per egg, form the sausage meat around the egg and then dip in egg and breadcrumbs, I bake them rather than fry them and I tend to have a lot of sausage meat so they look huge when cooked. I normally serve with a home made coleslaw or salad. Obviously they can also be eaten cold for lunch.