Single parent for 17 years so this is what I do:
Save whatever points your supermarket offers. Sainsbury’s is closest to me so I save all year to get money off the Christmas shop.
Find out when the reduced food is put on sale. Freeze it or batch cook it.
Do online surveys. Yougov and Prolific are good sites and you can “withdraw” your earnings from Prolific at any time.
Free school meals if entitled.
Use Quidco when changing your house/car insurance or other services. Then you get cash back in a few months time.
EBay things.
Use Freecycle.
Go to charity shops. Also, they’ll look out the back if you ask or even keep their eye out for things you need.
Repair cafes can mend stuff for you.
Library for books (!) but they also offer stuff for children like Lego clubs and reading challenges in the holidays.
Occasional foraging (chestnuts, blackberries etc) You can find apples at the moment. Also good for Christmas craft things.
Heat one room. We sit under a large duvet to watch tv. Hot water bottles in bed.
You used to be able to get cheap fleeces from IKEA (haven’t been in ages so not sure they still do these) and you can tack them along the top edge if your curtains as a thick lining.
Make a draught excluder sausage for the bottom of your front door.
Save cardboard boxes etc for craft projects. Useful if you can find someone in a job where they can bring you paper only printed on one side.
Free (ish) kids things we like: reading, pretending to be in a mobile library van (we’re v rural so apologies if you don’t know they exist!), cards and board games, baths with lots of toys in, making play dough, lego, murder in the dark type games, making tents, making treasure hunts with lots of clues on post it notes, going for a walk, cooking