Posted: Wed Dec 9, 2020 6:35pm
It very much depends on your budget and the original construction of the property. To do this properly, you would need to plasterboard your walls and use insulation between the walls and the board (internal thermal cladding). This is normally 100mm thick, so will make your rooms a bit smaller too! However, this would cost £000s.
There is 'thermal wallpaper' (e.g. Wallrock thermal liner), which would be a lot cheaper (but not as efficient). Both of these can be painted / papered over.
For the floor, the easiest solution, although maybe not the most desirable, is to have carpets with an insulating underlay. Otherwise, you'd need to lay a new floor (potentially over your existing floor if it's tiled) e.g. a laminate floor, with an insulation layer underneath.
In all cases, I'd suggest some expert advice as I'm not sure of the impact on condensation, etc. as most properties are built to 'breathe' and these may prevent / reduce that.
Depending on how cold you are (or feel) and for how much of the year, simply spending a bit more on gas for a heater and using rugs on the floor may be more cost effective...
Hope this helps!