Sometimes if I've defrosted something but don't fancy it, or think its going to go off i will cook the meal and put it in the fridge for the next day. Once id done a meal plan went to Aldi and the entire meat i needed for the week was reduced, so i cooked and prepared it all, froze some and fridged some. It worked out really well. Other than my kitchen looking like a bomb! Once you've cooked (assuming its well wrapped) it you've another 2 maybe 3 days.
I know some of these may seem obvious but i'll mention them anyway! As my budget doesn't stretch to fruit.
I try and cram as many vegetables into food as possible, so if I'm making a chilli or theres courgette, peppers, celery, carrots (sometimes grated) in it as well as the tomato.
I also do a lot of homemade coleslaw type things, literally finely chop (theres a hundred and one gadgets that will help if you get on with this) a red cabbage and red onion, lemon juice and olive oil, load of salt and pepper. Its lovely. To that you can add celeriac, celery, carrot, white cabbage, mustard seeds. Whatever you like. Or the traditional with mayo. The vegetables un prepared last longer then a tub of coleslaw.
If i do a stew i quite often serve it with mash one day and in a yorkshire pudding the next. Just stretches it out a bit more, again i cram it with vegetables (brussel sprout, curly kale, carrots, celery, swede) all cooked in so its tasty. I also do Delias braised red cabbage with it (and freeze half).
My budget doesn't really stretch to fruit, but you might be ok.
I know your asking for recipe ideas but the Lidl korma sauce (think its only 80p) is really nice and by the time you've bought yogurt at 40p and a tin of coconut milk its cost more than the jar. Chuck in some cauliflower, chicken and spinach and its more of a meal, plus its really quick and not much mess to clear up on a lazy day. Their premium pasta sauce is really nice (theres a few flavours), i think that ones 99p, again quick easy and not much clearing up.
Toad in the hole can be stretched with mash (frozen mash is nice and easy, although obviously doing your own will work out cheaper).