Ah well Mr Diamond Hell.....if you'd actually bothered to read the very first line of my original post you would have realised that it is indeed a motorcycle helmet and that I'll only be using it for trackdays and at the Pod RWYB days.
No, I read the title and the posts and still decided you had been a tw@t and bought a motorbike helmet to use in a car.
This means you're still available to be insulted, because you bought the wrong piece of safety equipment for the job, based on the fact that it's made of expensive carbon fibre and it will make you look 'cool'.