Jim S wrote:

I want to use a comparison site to, well, compare energy suppliers.
I know my total meter readings for the year, but I want to convert to kWh.

Multiplying m^3 by 11.2 will give you fag packet kWh

The 11.2 is arrived at by multiplying the atmospheric correction factor,
and the calorific value, if you want better accuracy use the values
which should be on your gas statement.