Help to analyze my Gas bills

Robin9

@Davlam0 following on from @Ildhund      Compare the serial numbers on the meter itself with the bill.

molerat

The May, Nov & Dec 22 gas bills are using metric meter calculations, from the Mar 23 bill onwards they are using imperial calculations meaning you are being charged 2.83 times the amount you should.  That is the simple fact at the root of the problem, the changing reads are just noise complicating the basic root cause.  All the bills need recalculating dividing the kWh by 2.83.  You really need to get it all laid out on a spreadsheet with the original meter reads, replacement reads, kWh & prices charged, that will make it much simpler to understand.

You need to raise a formal complaint that since Dec 22 they have been incorrectly charging you for an imperial meter when it is in fact a metric one hence overcharging by 2.83 times your actual use.  That is all you need to tell them just now and leave them to sort it out.  You give them 8 weeks to fix it then you take it to the ombudsman using those bills and the spreadsheet you have made as your evidence.