I am sure that many of the cars use some parts from abroad and up until they ended, I think only Reliant used 100% British parts............could be wrong though.
Splitting hairs about the origin of the components is silly I mean, the engine block contains Iron ore from the Ukraine so that BMW you thought was German ain't right! There are a lot of cars built, designed and sold in Britain by British engineers and designers, who's parent companies are foriegn but does that make them less British. I mean take the quinessantially British Ford escort for example!