Maybe I'm being thick, but I simply don't get why people think that it can be cheaper to keep a house constantly heated than to only heat it when you need to.
While a house is hot inside, it is leaking energy out to the outside. This is true in any real house unless it's hotter outside than in. The effectiveness of your insulation affects how much heat you loss. The thermal mass in the structure of your building affects how long (for a given heat source) or how much energy it takes to heat it up. But, SURELY, the hotter your house is inside, the greater the thermal gradient to outside, so the higher the (absolute) heat loss is.
If I turn my heating off while I'm out for the day, then I will lose less heat energy during that day than if I left it on. The only way that it can possibly end up costing me more, is if my heat source works less efficiently when delivering a high rate of heat input (whilst warming the house up from cold) than in a state of "keeping it warm". Modern condensing boilers DO work a bit more efficiently at lower revs, so to speak, but not by THAT much. And anyway a cleverer system would be to figure out that if you're home from work at 7, then it's better for the heating to come on at 6 with a flow temp of, say, 40C, rather than at 6:30 with a flow temp of 60C. Or equivalently, for a clever operator to simply turn down the temperature setting on his dumb system and wait longer for the house to warm up.
I'm thinking of getting a Honeywell Evohome setup (wireless programmable TRVs, centrally / remotely programmed and controlled) so that I can also only heat the rooms that I want to heat, for both comfort and economy benefits. E.g. I can set it so that little kids' rooms won't drop below 17C overnight in winter, without the kitchen being heated at 3am, I can set it so that bedrooms are free to get chilly during the day, and with one press I can set it to all switch to economy mode if I'm off out for the day / weekend whatever. That's the plan, anyway. Not cheap though, so not sure if it'll pay for itself in its lifetime (current set-up already fairly efficient).