nick1austin wrote:The petrol/EV argument basically boils down to whose figures you believe
No it boils down to where you are drawing the boundaries of the system.
You are following the EV manufacturer's route of just looking at the construction and destruction of the vehicle plus any in-use emissions. You are totally ignoring the CO2 cost of generating the electricity you are using. You quote 30% efficiency for a petrol engine, well electricity generation and distribution is what 18% at best? And since our primary source of leccy in the UK is coal-fired power stations then the CO2 "used" by an electric car far outweighs that of a petrol or diesel car.
In France the comparison is slightly better (since most of their leccy is nuclear generated) but even here an EV exceeds a normal car over the whole lifecycle.
If you are interested in working it out for yourself rather than just picking someone else's figures to "believe", then BMW published the results of their typically Teutonic testing and analysis.