If you are healthy and active and don't have any elderly relatives living with you, you can turn down your room thermostat a couple of degrees and just move around more and keep active by doing house or yard work. Heating in a home doesn't actually heat you much, it justs prevents you cooling down as quickly. The only way to really get warm is to be active.
Wear more clothes.
Exercise. This will keep you warm for hours and you can turn down the heating.
Beef up the insulation in your home to cut down on heat loss. The insulation in the loft can be upgraded by using thicker material.
Use localized heating sources such as radiant, fan or convector heaters when doing sedentary work such as sitting at a PC.
There are more tips on energy saving in my hub here: