That would be me, but there is an easy way out - release the manual/parts books. And they have still got time.
Going to law in the UK is a tricky business; the costs can easily spiral out of control and contingent fee agreements are not that common. For consumer law matters I have litigation insurance.
As for dealers worried about their margins. I, like most home hobbyists don't have a 2 or 4 post lift, I'm over 60, changing engines or gearboxes is not an ambition, I just want the assurance that routine servicing and some modifications are done to a quality, not a book time. They will probably still see the vehicle annually! (Although at this rate, I have no idea where!?)