Mr D - can you turn off the central heating radiators in the rooms you dont need heating?.... and INSULATE big style!
Floor to ceiling thick curtains, which get drawn a soon as light fades.
Thick door curtains behind exterior doors.
Extra loft insulation (goes without saying that one)
Sausage shaped draught excluders at the base of doors
Draughtproofing strips for doors and windows
Cavity wall insulation is expensive and when my landlord (was council) put it in last year there was one wall that they couldnt do because it had no cavity. It is the wall that is in the communal stairwell. The stairwell exterior doors are open in daylight all year round to let tenants cats come and go, so that wall was a problem - it always was cold to touch because it was conducting heat out.
I found Thermilate paint additive and used it on that wall and it no longer is cold to the touch because it now relects heat back into the room. I am so impressed with Thermilate that I have been adding it to ALL the wall paint I use when redecorating and have used it on 2 ceilings (will use it on the other ceilings too when i get the energy to do them)
Insulating Paint Additive, Insulating Paint, Paint Insulation, Energy Saving Paint