Thanks - I am also already trying that. In the meantime I got some response: According to the PoultryClubSA there are no Dorking breeders left in South Africa 
Someone else told me, that there are only few project/starter birds in not very good quality from UK or Holland. They asked me to bring them eggs.

Someone else told me, that there are only few project/starter birds in not very good quality from UK or Holland. They asked me to bring them eggs.