I bought chicken thighs in lidl the other day, 600g was about 4 quid, slow cooked down with cheap chopped veg like roots, or baked slowly with herbs and spices out of the cupboard, with potatoes or whatever
Dhal has to be the cheapest, bag of red lentils, spices, onion, soffrito, I put cherry tomatoes in mine but you dont bhave to, frozen spinach is a lot cheaper than fresh, in fact most frozen fruit and veg is cheaper than fresh and much 'fresher'.
Fabada which is Spanish white bean stew, butter beans, cooked for a long time, chuck the Aldi pork belly strips in so you get a porky flavoursome broth that cooks the beans, cook for a long time, chuck in some cheap veg/roots/onions and smoked paprika, serve with potatoes or rice but potatoes are cheaper
If possible dried beans and pulses/lentils are much much cheaper, although you do need to prep by soaking and I never remember to get them out
Tinned fish like sardines/pilchards/sild, serve with pasta or potatoes or on toast with cheese
Egg on toast, beans on toast, nothing wrong with that as a meal.
Soups with lots of bread, cheeses, ham.