I don't shoot any slide film anymore, since the one local semi decent lab here in Bloemfontein has stopped E6 a few years ago (and things are looking worse as they do not want to, but can, process my 120 C41 film, citing something to the effect that they have little control over the 120 but 35mm is fine.

There are labs in the larger cities that still handle E6 processing

Sandton, Johannesburg: http://www.thergbpixellab.co.za/

Cape Town: http://www.ormsdirect.co.za/ (under services, they are a photographic store with processing facilities, sadly they sell very little traditional photographic materials)

Durban: http://www.fotomax.co.za/pages/print.html

there are probably more that I do not know about