Being born in SA, I can say that all RHD 3 series have been built in SA for many years. I'd rather my car was assembled in Germany, but at the end of the day it isn't really an issue. Components are the same and good diligent labour in SA.
Merc also have most RHD cars built in SA plant
BMW F80 M3 DCT - Silverstone II - AA Mids, Active 8 tune