I have also asked this on this site, but I didn't get any real answer (just a few suggestions to wear more).
I am afraid I can't really answer the question. HOWEVER, following large gas bills, I did get my house insulated and draught proofed, and I find now I can put the heating on for half an hour if needed (normal economy temp) and it retains the warmth for far longer - even then it doesn't really get cold. Prior to getting this done, I could have it on full wack for hours, turn it off, and then find I had to turn it on again later.
I think when winter properly comes I shall just have it on low for most of the evening (when I'm in most) but the point I am making is that those insulation measures are actually worth it, so if you need it, consider it.