From my understanding of the way central heating a house works, it's better to keep it on for a lower temperature all the time than a high temp for short periods of time. Having it on a lower but constant temp allows the actual fabric of the house, the bricks etc to warm up, thus getting a radiating effect. It also pays to check for draughts from windows, doors, floorboards etc and try to block these up although not all as a house needs to breath to allow moisture to escape otherwise you end up with condensation problems.