Help - new home is freezing

[Tulipdays]

I've recently moved into a 1920s ground floor maisonette, it's end of terrace and has a large outrigger with a flat roof. The flat is absolutely freezing, obviously once the heating is on, it's fine but also loses heat very quickly once the resting goes off - artic again after 30 minutes or so. The flat has a very long corridor and also an understairs cupboard which is breezy to say the least. The flooring leaves a lot to be desired (vinyl tiles with no apparent underlay) throughout the flat.

Suggestions please on what to do. Spending on money on insulation is an option but I'm clueless where to begin.

You need to insulate. Do you own it?

Big heavy curtains in front of doors, sausage dogs in front of the doors, insultation under the floor board, insulting board in the cupboard under the stairs - but allow for some ventilation still.

If you own it you may need to get someone to insulate the roof of what I'm assuming is an extension. Replace tiles with carpet with underlay.

In the short term?
A long runner for the hall. See if you can add a draught excluder brush to the bottom of the door.
Is the flat roof extension separated by a door? If not add a heavy curtain.
Try and keep the heat in your key rooms so insulating tape if you have draughts in Windows. Use thick curtains.
Watch furniture against outside walls. You may get damp from condensation if there's no air circulation.

Is it leasehold or freehold?

Thanks for the replies.

I own it, long lease and freeholder has little interest so everything is 50-50 split with the upstairs leaseholder who rents out the upstairs flat.

Yes I need short term measures, thank you for the suggestions, I'm not a lover of carpet but feel at this point I may need to bite the bullet and install some cosy thick carpet in the horrendously long hallway. I was thinking to get an internal door built to cut the hallway in half - would that help?

The skirting boards are ice cold and some areas of the flooring have gaps so I will also go around with a caulk gun. Does anyone have opinions on insulating under the floorboards? Is it a massive and expensive job?

To clarify, the outrigger appears to be an extension but is two storeys with a flat roof and not a recent one at all as the rendering is all original and is the same as neighbouring houses. I suppose at one point the "extensions" were all added at once.

Having serious buyers regret I must admit!

@Tulipdays

I've recently moved into a 1920s ground floor maisonette, it's end of terrace and has a large outrigger with a flat roof. The flat is absolutely freezing, obviously once the heating is on, it's fine but also loses heat very quickly once the resting goes off - artic again after 30 minutes or so. The flat has a very long corridor and also an understairs cupboard which is breezy to say the least. The flooring leaves a lot to be desired (vinyl tiles with no apparent underlay) throughout the flat.

Suggestions please on what to do. Spending on money on insulation is an option but I'm clueless where to begin.

Under floor heating. When we stay at holiday places, they invariably have underfloor heating and its unbearably hot. Its clearly quite effective

Thick curtain over the front door will help if it'd drafty.

Do you have slippers?

Get lots of rugs.

You can buy thermal film I think for windows. And also thermal blinds and curtains.