I have a few tips.
Buy dry foods in bulk when you can. I just bought 10kg rice for £7 at tesco.
When I use mince, I use half mince, half lentils.
I make a rice porridge - 1 part rice to 8 parts water plus: spring onion, ginger, garlic, soy sauce, and if I have money, then a chicken breast. Cook it all on a really low heat in a saucepan for about 2 hours. For me, it is a bit of a comfort food.
Homemade potato wedges with my healthy extra cheese (mozzarella or cheddar are good) and gravy.
I cook in batches and make 4-8 portions per meal, then freeze them.
Legumes (dried) are your friend. They require a little more prep, but are crazy cheap.
The mushy pea curry is actually good. It's just a pea and bean curry - tin mushy peas, tin baked beans, tin chopped tomatoes, curry powder and simmer for a few minutes.
Spices and herbs are your friend. I used to use fat for flavour, but now am focussing more on herbs and spices. invest in some (packs of fresh herbs can be frozen, spices last for ages)and experiment.