When I think back to my childhood where we only had one coal fire in the house and no central heating, the answer to keeping warm was to wear lots of layers of light clothing, and now energy prices are become so expensive I think we're all going to have to re-discover this method. If you're active and out all day I'd switch it on for an hour or so in the morning, and then again in the evenings. If your home is really well insulated the house will retain much of its heat.(Cavity wall insulation and extra loft insulation will make a world of difference to your heating bills. Draw the curtains in all rooms as soon as it gets dark to keep the heat in, even if you have double glazed windows. And in the evening, stand up in all the commercial TV breaks and do a few exercises. It will help keep the circulation going !