Disclaimer: I know very little about central heating but I saw this tip on the Octopus app this week.
Also, probably everyone already knew this already except me 😂
Basically it involves turning down the flow temperature on your combi boiler, which should mean you use less gas (see attachment)
I have reset mine (both were on 80) and I can see in the smart meter that I am already using a lot less.
So if this helps anyone lower their bill slightly, hurrah, because energy prices are scary high at the moment.