Well, maybe 
I just checked our combi boiler settings, based on another thread.
www.protechboilers.co.uk/guides/your-combi-boilers-ideal-temperature-for-central-heating#/
I was suprised to find ours are already set at 10 - 15degrees lower, mid 50s. Maybe that is why our gas is less than expected. I could easily turn the water down a bit more too.
Our biggest saving must be how we shop and cook. We both work all over the place and so always have to pass a supermarket on the way home. So we tend to food shop daily. We have large storecupboard shops 2 or 3 times a year when we buy all the cans we can find at Aldi or Lidl.
So we buy food most days and we always buy to bulk / batch cook. So one spag bol becomes enough for a month. That kind of thing. This Sunday was a beef stew, cost about £8 to make and has frozen back in largeish portions to feed 10 more meals, so 12 in all - actually no 14. I left it to it and 'mature' so we has some last night too. We just have to add boiled potatoes or bread.
Clothes are second hand for me. I only buy new underwear and shoes. DH trashes his at work so he buys cheap tshirts and semi decent jeans. We wear the knackered tshirts at home once they are too far gone for his work. And even then they have a next life as cleaning cloths. Mine tend to eventually (say 10 years later) get cut up and reused for other clothes patching or my craft business.
Our fridge would usually be almost empty so I keep all sorts of things in there that aren't necessary but do no harm. I aim to keep it 3/4 full at all time. Use it to defrost food slowly and I keep freezer blocks in any empty freezer drawers to keep that more efficient too. They can go back into the fridge when not needed, they just cycle round and round.
I do shop in farm shops, most days. We buy as much locally produced fruit, veg and meat as we can. But as we only buy exactly what we need we don't waste anything and, as it is all local and seasonal, there are very few travel miles. Sometimes the longest distance something has travelled is between the shop and our house. That doesn't mean we don't have out of season or well travelled stuff, just that it is a treat, not a daily staple.
And I grow salad stuff. Recycle spring onions, old dried peas for pea shoots - I facebook for old out of date packets of seeds and then treat it all as cut and come again, even if it doesn't
Cherry tomatoes and chillies too. I grow chillies every couple of years and freeze them all back. They last forever in the freezer. I keep ginger root in the freezer too. We use a lot of it and it is easier to shave off what you want - one of those microblade graters is really handy, makes a small amount of parmesan go a long way too.
www.lovethegarden.com/uk-en/growing-guide/how-grow-spring-onion#:~:text=Growing%20spring%20onions%20in%20water&text=Choose%20spring%20onions%20that%20have,jar%20in%20a%20sunny%20position.
God, so many things. A bag in the freezer for old tomatoes and peppers. Gets made into tomato soup of bolognese/pizza sauce. We really do make chicken stock and use that for soup or base of many sauces, graviy etc. Odds and ends of bread get kept, breadcrumbs for all sorts of things, croutons too.
We just don't waste anything. We put less than a small food caddy bag put every week. Tea bags and coffee grounds get kept for cloth / paper dyeing and compost - until I get sick of it, then it goes to the community composter.
I know there is more. We have done this for decades. Our next step is the house, more insulation and better fuel efficiency. I am looking at that now. It will have to be cheap, I will see if there is a local maker, or some in the recycling centre, before I order new.
Surely there is a good book on this somehwere.? One with real, doable things rather than the pie in the sky stuff that gets touted on all those lifestyle programmes.