We have a much warmer house for far less money than our old gas boiler, as it only heats water on demand, so when you turn your tap on or the room thermostat (wireless) tells the boiler that the temperature has gone down below the set level. There are a series of set levels depending on the time of day.
So when my son (an engineer with the council) has to get up on "early turn" at 4.30 in the morning, he tells the thermostat to come on an hour earlier than usual, for example. It's easy to change apparently, but son is very possessive of the thermostat, feels it's Man's Work and gets really funny if I touch it.
Sometimes he forgets that his mum has used a computer etc. longer than him!!!