Mike Dee
On 4th September, you asked for advice about estimating your future gas bills. I’m sorry that no-one has replied to you until now but there’s no simple, accurate answer to your question so that’s the likely reason for the lack of response.
The relation between “units” consumed and the payment demanded is complicated and depends on your supplier’s tariff (especially on whether it involves a “Standing Charge”), on the type of meter you have and on other more minor variables.
If you still want advice, send another post to give as much detail as you can. You should be able to get it all from any previous gas bill but, as far as the meter is concerned, the essential thing is the size of its “units”; a close look at its face should tell you whether it is measuring in units of “100 cubic feet” or units of “1 cubic metre”.
If you can also say roughly how many units you generally use in each quarter (that’s likely to vary a good deal from one season to another), that will help, particularly if a “Standing Charge” applies.