What is your concern: High heating bills or a feeling the house feels cold?
Whilst interrelated, they might have different solutions.
I would start with the low cost things that can make a difference.
-as mentioned above, reduce any draughts. Check all your doors and windows for draughts and adjust as necessary. An incense stick can help, or just feeling with hands on a cold day when the heating is on. Check window frames are sealed where they meet brickwork.
Appears to be the case from inside, I guess I need to check outside also.
-do you have TRVs? - they allow more control over different rooms.
Yes, I have TRV on every rad, and I also have a reflective foil on most rads.
-do you have good fitting curtains or blinds for the key rooms, like lounge, kitchen etc.
Yes we do, even though they dont look nice at all. Once the works are done, the plan is to have shutters. I dont know what they are like.
-do you have insulated and draught sealed loft hatch?
Yes we do, this was done when loft was insulated.
-a bungalow has a long run of soffits and fascias, make sure your loft insulation reaches right across the ceiling and jojns the brickwork, so that any eves ventilation is going up to the roof, not blowing onto the ceiling.
I do not live in a bungalow.
When you have your extension done, get the insulation sorted out in kitchen and lounge.