Under floor insulation

[TooCloseToTheProject]

Our living room and living room floor is always freezing compared to the dining room (which has no heating but only 1 small external wall). We have a cellar and despite using a draft excluder I think the draft comes up and goes across the corridor to the living room. I wondered if a quick fix would be to put a carpet over the cellar hatch. Also wondered if we could just insulate underneath the living room floor, cupboard under the stairs with the hatch and corridor between the two or would that push the draft to the dining room?

Hubby thinks the cold/draft comes from one of the external walls but we can't have it insulated from what I've read. Any advice appreciated and thoughts on how expensive having insulation fitted might be.

Just to add we have a gas fire and central heating in the living. Fire warms up the room quickly but I find that the floor is still really cold.

You'll probably find the cold air is actually coming through the floorboards and making the floor covering cold. On the plus side this should indicate the flow of air is good!
It also sounds like several factors at play so complete one job then move to the next if you need to. Don;t understand why you can't further insulate your wall though?
Insulation can be applied externally or internally and obviously in between walls if you have a cavity.

If you have a cellar, and when you look up, you can see the underside of the floor, it is easy to insulate with mineral wool pushed between the joists and retained by mesh. Use the type treated with Ecose that does not shed irritant dust and fibres (it is brown, not yellow)

Pay extra attention round the edges of the room where most draughts come up under the skirting board. If you can't do the whole room, do the edges first.

If you have a hatch, check it fits the battens closely all round, and add draughtproofing strip.

Mineral wool is better for this than rigid board because it can be squashed to a tight fit. It is difficult to cut rigid boards so precisely.

Additionally, mineral wool does not burn or emit toxic fumes in a fire.

Heat loss through a floor is almost all by draughts, so the insulation does not need to be as thick as in a loft. 100mm will be plenty.

It is also possible to lay it from above by lifting the floorboards, but this is much more work.

Clean out all subfloor airbricks and ensure the insulation cannot obstruct them.

Thank you both for the advice! Sorry, yes I meant we haven't got cavity walls.

btw you mentioned you have a gas fire. This draws air from the room for combustion, and sends it up the chimney mixed with warm air. This will create a certain amount of draught as it draws more air into the room. Open fireplaces and older fires can send a lot of warm air up the chimney. More modern ones, sealed and with a glass front, not so much but look less traditional.