Ok, I've had a think about this properly and also chatted to Blastoise186 about it. He's in agreement that a Burns Test may help to identify any possible faults. You'll definitely want to do this now
before attempting to request any kind of Meter Exchange, as doing that will prevent you from resolving this issue.
While I'm not usually a fan of copy/pasting stuff, providing the instructions regarding Creep Tests or Burns Tests is complicated to get right, so this is one of the few things I will copy something over from my notes.
Here's how to do a Burns Test. This is a quick test and only takes a few minutes, but you need to be able to get to all your gas appliances and your gas meter to do this one. Here's what to do.
- Turn off ALL gas appliances, the boiler and everything else that uses gas on your supply
- Wait for around 30 minutes to let things calm down and for the gas meter to completely catch up
- Check your gas meter reading and make a note of it
- Turn on just one gas appliance - a single ring on your gas cooker is usually the best option
- Monitor the readings on your gas meter for five to ten minutes. You must do this on the meter itself. Make notes of the current reading every 60 seconds during the test
- Shut off the gas appliance you fired up
- Check the gas meter reading again
- Restore your gas appliances to normal service once you're done
The reading should only go up by a few units during the test. If it seems to be clocking up excessively quickly, this suggests there might be a fault. A Burns Test isn't perfect, but you'll be surprised how well it works. If you suspect an inaccurate or faulty meter after doing this, you'll want to call for help and request a Meter Accuracy Test (it's an OFMAT for a gas meter). These are not free and you'll be asked to pay the job fee upfront (usually around £160 or so).
If the test confirms the meter is faulty, you will get the fee refunded, the meter will be replaced and you should get refunded for any usage that you didn't actually use if the meter clocked too fast. Recalculations don't occur if the clocking was too slow. While electric meters are only replaced if they fail the MAT, gas meters are usually replaced anyway as part of an OFMAT process. Be advised that over 80% of OFMAT tests come back with no fault and you'll sacrifice the fee in those cases.
The fact you've got an imperial meter also makes things more complicated. But I think a Burns Test should still work anyway despite this. To me, it appears that the gas meter you've got has probably gone round the clock and back multiple times since 1993 and is probably wearing out, which might be a contributing factor here. If you get a replacement gas meter, it'll almost certainly be a more modern one that uses metric (cubic metres) rather than imperial (cubic feet) measurements, which are generally said to be more accurate anyway. The conversion to kWh isn't done by the meter, but by the billing system after you submit the meter readings.
On top of that, I somehow get the feeling you're being billed based on cubic metres rather than cubic feet. If this is the case, your bills are incorrect and will need to be regenerated after being switched to imperial. If you've been overcharged as a result, you're entitled to a full refund of ALL overpayments for the entire time you've been at the property, up until the issue is fixed.
Hope this helps. I'll be here if you get stuck.