Just in case anyone else was thinking about doing similar here is the reponse I have had from the CAA in South Africa to the same question.
Dear Mr Mortimer
The information you received was indeed incorrect.
You would have to follow the route of applying to the Air Licensing Council of South Africa for a Foreign Operators Licence. Once this is granted you will have to follow the route of having an Operators Manual approved by the SA CAA and apply for the issuing of an AOC. The UK pilots will also have to validate their CPL's for South Africa
Now another question.....
Anyone had experience of applying for a foreign operators licence???