Mid terrace victorian 5 bedroom house Gas annual 27000kWh

[superpossible]

Hi looking for some advice on reducing my gas bill.
Currently my annual estimate for gas is £2000. Our usage is far greater than the average for a 5 bedroom house and I'd like to get to the bottom of this.
We have a new boiler,under floor insulation, a converted loft with insulation. Upstairs is warm but downstairs is not esp the kitchen which is part of an extension - it has its own latch but that does have insulation.
I think these might be the main culprits

1. kitchen and bathroom downstairs have 15+ Yr old windows and the bathroom ones are draughty - we will replace these once winter has gone
2. our front door (upvc) also feels cold when you stand near it - not sure how to fix this as the doors really aren't that old.

Are there any other changes we can make? Our thermostat is set to 20 degrees on manual mode all day long. When the temp drops to 18 ish we do notice it and find it uncomfortable. Atm we are using around 12m3 of gas according to our smart meter.

TIA!

I don't think that your bill is excessive. We have similar arrangements and our annual bill is £2400. My friend has a smaller Victorian end terrace and they are paying more. We do use throws in the evening and they definitely make a difference. DH has suggested triple glazing but I'm not sure that it's worth it. It will be interesting to hear what others say.

Roller blinds to each window AND curtains. The double layer really helps reduce draughts. Curtain over external doors too.
Heating only on when the house is fully occupied. If I'm WFH I just have a little electric heater.

Do you have the heating on all day long seven days a week? That is probably more than average, so your costs will be higher. I work from home and only have it on in the morning for a couple of hours and evening for about four hours.

I used thermal imaging to identify the cold spots.

For me the price of the camera was justifiable because I can use it for work.

You are looking at maybe £200.

There are normally a lot of small things you can do to improve things, draft excluders on doors, curtains etc. But a camera will really help you find where the real cold spots are. Then of course it is a matter of how cheap it is to fix them.

I do think that in a house of that age and that size you really have to be thinking of a heat the rooms you are in and not the rooms you aren't strategy. Keeping the whole place at 20C is going to cost ££££ as you are finding out. If you can't do this then maybe TRVs on the rooms you use less would help.

Your 12m3 of gas over 24 hours corresponds to a constant heat leak of about 5.5kW.