Please can some one tell me which is most efficient if you want to get the
central heating up to say 22 degrees in time to get up in the morning....

Leave the thermostat on 22 degrees and have it come on earlier for longer
or
Put it on 26 &/or turn up heater temperature and let it come on later.

I've puzzled so much I'v econvinced myself both ways, but there must be a
scientific answer...
cheers