If I understand you correctly, you have not stated, or do not know, the ACTUAL gas usage from the meter, for a 12-month period or for a winter month.
Payments and projections are not reliable.
Have you got your old gas bills, and do they show accurate (not estimated) meter readings? If not, have a look on your supplier's website.
about 25621.7 kwh for the 12 months.
As for a Winter month, the bill of Jan 17 - Feb 19 showed usage of 4242 kwh for gas.
So I think your 12 month usage would cost about £1250 plus standing charge.
4242 divided by 60 days is 70 kWh per day. About 6 cu.m per day which is not unusual for cold weather, depending how warm you like the house, if you have CWI, if you keep the internal doors open, etc.
Jan, Feb.
Did you mean for a single month?
You say you have actually USED 25621Kw?Yes I kept all the bills.
The first bill I have showed a starting reading of 0 (when we had the new meter installed at the end of Sep last year). Today it reads 2295.07 m3 which I make to be about 25621.7 kwh for the 12 months.
As for a Winter month, the bill of Jan 17 - Feb 19 showed usage of 4242 kwh for gas.
You say you have actually USED 25621Kw?
At 3p per kWh, that is less than £700 per year. Plus, of course, a standing charge - which can be about £200
I track my meter readings and note average daily use per month.
Winter is 6 or 7 cu.m per day
Summer is 0.5 to 1 cu.m per day