Switch to energy saving light bulbs has got to be a great move (switching an old 100W bulb with a green 200W bulb will save you £7 a year, which may not seem like much until you add up how many light bulbs you have in your house. I don't like energy saving bulbs them on aesthetic grounds but I have been turned by Hulgers light bulbs. Hulger’s Plumen lightbulb uses 80% less energy, last 8 times longer and look amazing.
Think soft furnishings.
Velvet Drapes, carpeted floors, will all help to retain heat. Especially in old houses with original windows. If you have bare wood, timber floors can be insulated by laying mineral wool under the floorboards. Or for some added heat go Blue Peter style and fit foil behind radiators. Half the heat from most radiators goes straight out the back and, usually, so fit reflective foil panels behind your radiators.
Don't buy new, recycle what you have, recover, repaint or buy vintage. I have never know what to tell clients to do with old carpets on projects where we are supplying new carpets. But I have now found companies which will take your old carpets and use the waste to create new plastics products.