There are 2 types of gas meter. One that measures in cubic feet (known as an imperial meter) and one that measures in cubic meters (known as metric). If you have m3 on your meter, this means that you have a metric meter. However, if you have a metric meter, and you are being charged as an imperial meter on your bill, then yes you have been overcharged. The way to determine if you are being billed is by looking at your recent charges on your gas bill. For example ONLY, if you have used 100 units of gas, you need to convert this to kilowatt hours. If you have a metric meter, you would follow the instructions on your bill on how to convert your 100 units of gas to kilowatt hours, for Example 100 units x the caloric value of approx 39.0 x the correction value usually 1.022640 then divided the full sum into 3.6. So 100 units x 39.0 x 1.022640 / 3.6 = 1107 kwh which is then multiplied by your unit price. So you gas bill would show that you have used 100 gas units, which is converted into 1107 kilowatt hours x your unit price of approx 3.39 pence = £37.55. HOWEVER, if you are being billed as having an imperial meter, you would take your 100 units of gas, and multiply this by 2.83 (as shown on how to calculate your gas usage that should be shown on your bill) x 39.0 x 1.022640 / 3.6 = 3135 kwh x unit price of 3.39 pence = £106.27. Therefore if you have a metric meter, and your gas supplier are charging you for an imperial meter, yes you would be overcharged by approximately 3 times.
Hope this is not too confusing for you.
(By the way, I work for one of the top 6 gas and electricity suppliers and not British Gas) and know my stuff.
