Do you have Citizen's Advice Bureaux where you are?
Or alternatively, the reference section of the library,(merely as a good place to start, not finish), to find out what you might be able to claim.
One thing that's helped me greatly is to get lots of low=energy bulbs. Boy they make a fuel bill difference.
Now you're retired, what would you just love to do? List 20, and see if there might not be money to be made in 2 of them. And don't make the making money the point but a happy byproduct.
"I will find a way, or make a way." (Some idiot called Walter Raleigh, i think)