I posted a topic around a month ago about my gas bill being in hcf (hundreds of cubic feet) and my gas meter measuring cubic metres.
I've just had a revised bill from my gas supplier: they've scrapped all charges over the last two years and recalculated using the correct units.
The up-shot is, I've gone from being =A31500 in arrears to =A3250 in arrears (I did suspect my monthly direct debit should have been upped).
So, the moral of this tale is: get to understand how your gas bill is calculated.