Morning, I have family, recruited by a crown agent, from Rothbury area NBL coming to work in South Africa on the Natal Government Railways in 1885. I understand that workers with certain skills were targeted, transport costs paid. My ggrandfather worked out his time, changed jobs on the railways and never went back, according to the research I managed to find, many did not return to UK. Had a quick look at FS in South Africa - Duncan popular surname, also some Donkin's - perhaps worth a look?
Regards
Catherine