To clarify: MG Rover was the last wholly British owned volume car manufacturer before its closure in 2005. Yet I believe the UK is still the 3rd or 4th biggest car producing manufacturer in the EU, with significant production plants across the UK from Nissan, Toyota, BMW and Vauxhall.

Is the contribution to UK's GDP and the general financial benefit to the economy any less because these plants are owned by overseas companies?

I can understand that their commitment and loyalty to the UK may be more ambiguous than a British company, and that if redundancies have to be made then the UK plant maybe more vulnerable as illustrated by the Peugot Ryton plant for example. But this aside, as long as the plant remains here and is employing people and producing vehicles that sell, does it make a difference to the UK economy if the parent company is British or from overseas?