@DuaLipaSuction
Great advice mint but I'm not sure about the water meter? Would it be worth the OP doing that if there are 5 of them?
No. Don't get a water meter OP. Ask the water company if there's any discount for those on a low income and see if you qualify.
Porridge oats and potatoes are the foods that fill you up the cheapest way without being unhealthy. Buy a sack of potatoes and large bag unbranded porridge. Cheese sandwiches too, family size blocks of cheese, add a little salad if there's anything left over.
If you're doing salad with a meal get the separate ingredients and cut it up yourself, not a bag/tub salad. Pizza can be stretched to two portions by cutting in half and adding salad.
Frozen or tinned veg so you don't waste anything by it going off.
One tin soup, one tin mixed veg (drained), in a bowl and stir, 3 1/2 min in the microwave, split into two portions and add a couple slices of bread to each, makes a cheap meal.
Rice boiled with water can be put in soup to bulk it out too or added to a meal instead of potatoes. Home made rice pudding is a cheap and filling dessert. Boil the rice then simmer until soft, use 50/50 milk water (plenty), stirring constantly, add jam or sugar, serve.
Bake cakes, much cheaper than buying ready made, cook a pizza in the oven at the same time.
Get your washing done early and on the line by 9am if it's dry, especially if there's any sun or breeze it'll be dry by dark or 3/4 dry if there's no sun or breeze. T-shirt under jumper and vest for a base layer. Only wash your jumpers and jeans if they're dirty/smelly/1 week worn, whichever happens first.
Watch TV in the dark.
Hot water bottles in the beds, an extra blanket on top and only put the radiator on in bedroom half hour before going to bed, to take the chill off the room.
Humans lose a lot of heat through their heads so hoodies help. Blankets on sofas to put over yourselves makes a big difference. Look on Facebook selling pages for piles of them going cheap. Keep doors closed and only heat the living room, and the bathroom long enough to dry off the towels after use.
Plan your car journeys so you're going in eg a triangle or square round the roads, not going out then home several times per day. Saves miles.