My dad grew up just after the war when people were especially poor and he could never get out of the habit of saving his basin water for the next person to use to wash their hands instead of wasting it. Obviously stuff like that always seemed silly to me but UK has definetly been poor in energy etc. before now. Put your kettle water in a thermos if you somehow boil the whole kettle and only use a cup, it'll save a fair bit over a year. Tons of stuff like that, people got used to not doing it but it adds up. Not sure we are getting to the point growing your own spuds in the back garden is required, they arent too hard to grow so long as its not a rainy summer. Plant themselves for the next year if you miss a couple when harvesting
Not sure I'd want the hassle but you can put out the pilot light for however long and turn the gas off at the mains