A few years back I stopped being a supermarket snob and now do 99% of my grocery shop in Lidl/Aldi. Have literally saved thousands. Also, less choice, so easier to avoid impulse buys.
After a shockingly high gas/electric bill in January (£178 vs what I used to pay -£65), I aimed to not have the heating on. I wear lots of layers and invested in an electric blanket for emergencies! Also only put the hot water on for 1 hour per day, so just enough for showers. Feb bill was ‘just’ £75. I live on my own, and know this wouldn’t be possible if I still had kids at home.
If you have space, try and grow your own salad and veg. I only started doing this myself last year (surprisingly easy, even for this novice!), and rarely had to buy anything fresh at the supermarket. Excess stuff can generally be blanched and frozen, or made into meals….
Get a slow cooker - make your own eg soups, stews etc and batch freeze.
I’ve just ditched Sky and the TV licence, as there’s more than enough for me on Netflix (much cheaper) or YouTube (free).