Hi,
I am in the middle of validating my UK licence at the moment in Cape Town.
You need to
convert your radio licence - about 30R
Pass an open book airlaw exam
Pass a flying test involving the usual stuff plus a cross country element
Fill out and send the form to Pretoria.
I am doing all this with Delta 200 at Cape Town Intl Airport.
Very friendly outfit with Cessna 150 at about £35/hr.
Hope this helps