I have about 3000Kw worth of heat producing heaters in the livingroom, still freezing with new double glazing.
My mate duncan went out on the **** the other night, left his window to his bedroom open. When he got home at 5-6 in the morning, his bed covers were frosted solid!
This was in Fife.
No swearing
Gilly
Assuming you own the place and haven't already, get cavity wall and loft insulation.
We noticed a major improvement when we had the walls done, and the loft insulation topped up (double glazing cuts down on the heat loss through windows, and drafts from them but doesn't help much if you're losing a lot of heat through the walls/loft).