British Gas replacing my gas meter

mccaba

My smart gas meter stopped updating sometime in January, and by that I mean the meter itself, not the monitor.    I reported it to BG and was told it was a temporary issue and it would restart within few days.  It didn't.  I mentioned it to the BG engineer during the annual boiler service, and he said it was faulty and to report it.  I did so, and was given the run around for several weeks, " ...it's not faulty", ...." it will update automatically".   It took an official complaint last week to get BG to finally accept the meter was faulty, and it is being replaced with a standard meter on Friday.   I understand there are no smart meters available in my area and it will be swapped back at a later stage.  

Can anyone in the know tell me how will my next gas bill should be calculated  ?     Both I and BG have photographic evidence of the meter reading as it stands.    I am willing to pay for gas consumed, but how will we establish that ?

Thanks
Andrew