Help me out please

So we move in to our new home on the 8th obviously with it being a new build and everything being brand new the boiler and heating system u can set it so it stays at a certain temperature throughout the whole house so if it drops the boiler automatically kicks in till it’s back up to the temp u want then turns it’s self back of, well my question is is it cheaper to keep it on like that for it to do it when it needs to or for us to just turn it on as and when we want to use it if it’s really cold ?

Also which electricity and gas company you with ours is rubbish maybe have heating on 2 hours a day and we just got a bill for £180 ( some day it wasn’t even on cos was mild ) tia