No, the shown cars aren't made by small car-companies, all of them are derivates, resp. just rebagded cars from bigger companies, assembled somewhere.

Passport and Asuna are Opel Kadett E-derivates, like Vauxhall Astra, Pontiac LeMans, Daewoo and many more.
The "Automobile Craiova" is known as Olcit, the Romanian derivate of the Citroen Visa.

And "Sterling" was IMHO just a more exclusive trim-line of Rover.