For me (Northern Ireland), our most famous car was the DeLorean DMC12.
John DeLorean built this car in Belfast. Sales flopped and he decided to start selling cocaine so he had extra cash to inject into the business to save it but he got caught. There’s many good documentaries about it. Some of the Irish look on him as a drug dealer, some look on him as a good guy who tried to save jobs. It all depends on who you talk to.
My second nomination is the Clan Crusader. I know most of you will never have heard of it but it was a Hillman Imp based kit car. Massively successful on the hillclimb scene but outside of pikes peak, most people know nothing of hillclimbing.
We also had factories building Ford Sierras and Mk5 cortinas but that’s irrelevant in the grand scheme of things.