If you consolidated gas meters you could save £1,500 per year.

Your annual standing charges for 2 gas meters is £2,920. You can ask your energy company to combine meters into one which would reduce your standing charges in proportion to the number of meters, which could lead to a potential annual saving of £1,500. Over 10 years this could save you £15,000. The cost of consolidating one meter can be as low as £1,000. 

The opportunity to consolidate meters depends a little on the location of the meters, and works better if they are in close proximity. However, if one of the meters is on a differential tariff (economy 7) and is just for storage heater heating then the consolidation might not be economically viable. Consolidating meters may also reduce a more detailed understanding of energy consumption in different buildings, however non-mains connected sub meters can be cheaply installed if necessary with no standing charges.