whats cheaper...on 24/7 low or once eve and once morning?
that's a hard one to answer, iv experimented plenty, the problem is if the walls get cold, you spend most of your heat warming them up, high ceilings are also an issue.
anyhow, if ur only in your home say, 3 waking hours at night, and about the same in the morning, iv found putting it on the timer is cheaper, for when you wake up and get home.
however if you spend more time at home than work 24/7 is better, however for the first week or so (depending on insulation) it will be more expensive because your heat will be soaked up by ur sofa, carpets, walls and etc, but once your whole home reaches a steady temp, it will be cheaper and easyer to keep, but unfortunately it gets stuffy fast. and you end up opening windows.
i tend to be quite thrifty and i have draft proofed my sitting room door, turned off all radiators exept for my sitting room one. and i use an electric heater for 30min in the morning (timer) to get me out of bed
the kitchen gets heated when i cook (oven) and the shower soon warms the bathroom, so i only need one room to be warm. thats my cheapest way