I trained with these guys in 83 - brilliant - same instructions that are given to the British Police.
http://www.advanceddriver.co.za/about-us.html
The Porsche one last year was lots of fun, but it was more track racing than advanced skills (skiing and skidding is generally discouraged)
Depends on what you are looking for. A couple of years back I did the VW one. Skidpan, lunch and then a decent amount of laps around Kayalami. They teach you oversteer, understeer, turn the driver aids off, handbrake turns....and let you ruin their tyres.
Lots of fun. Not sure how it rates compared to other courses though.
Looking at mainly high performance driving