I've been banging on about this across loads of threads lately, but it will be our biggest "saving" this year, so I shall shamelessly repeat it in the hope it might help someone...
If you have a mortgage check when you're initial fixed period is up. You can lock in a new deal 3-6 months before your current fix ends. With interest rates going up the way they are, fixing now will be much cheaper than fixing in February. If your current provider will only let you lock in a new deal 3 months before the end of your current fix have a look at other providers.
We have a large family and were down to one income for a few years, so things were tight and we cut right back.
Food wise, we tried all the cheaper own brand/value foods first. We preferred lots of the swaps to the big brands. Swapped supermarkets to lidl which really helped too so long as you avoid the middle isle of doom. We rely more on pulses and eggs for protein than meat. Lots of people eat far too much meat.
Really hate food waste. Challenge yourself to get as close to zero as possible. Leftover mash and veg can be reshaped into potato cakes (can add a little milk if they are a bit dry to shape) and topped with a fried egg and served with baked beans for protein. There is another meal. Leftover pasta into pasta salad, leftover rice into egg fried rice (my teen loved loves this). Try to base meals on what's going out of date next. If you open the fridge all you see is red peppers google red pepper recipes and see if you can throw something together before taking something out of the freezer to defrost. Flat breads and naan are very easy to make and cost pennies, but can help to bulk out meals.
It's a bit of work, but really cut our food bill down this way, and you get to try lots of different recipes instead of the same fixed things.
Looking at Christmas, can you agree with other adults not to swap gifts and just to focus on the children? Or do secret santa with a budget in mind?
I agree with whoever mentioned turning the oven off a few minutes early. You can also leave the oven open once you're finished cooking (but watch out for small children) to let the heat into the room.
Make sure your house is well insulated. Check your loft. We got some great draft proofing tape that has sealed up a few windows for us. We packed up a now unused hole at the back of the tumble drier that was once intended for an older model of drier with an extraction tube, but is basically just a big hole in the wall letting all the hot air out and cold air in.
Be aware of what your highest electricity usage items are. Normally things that are cooling or heating. So washing machines, freezers, dishwashers, tumble driers, electric showers etc. Work out how to use them less.