Hi there Spitty
I think you will get the answers you need from the South Africa CAA, website
www.caa.co.za
If you have all the JAR ATPL exams I think you will be credited in SA with them except for airlaw and may be ops and procedures. You will need to the relevant flight tests to fly ZS regsitered aircraft.
As for the IR you can get quotes from the following schools in Cape Town. I will give all three web addresses lest i be seen to be advertising.
Cape Areo Club -
www.capeaeroclub.co.za
Good Hope flying club -
www.ghfc.org.za
Delta 200 flying school -
www.delta200.co.za
ther are good schools in Port Elizabeth and also there is the well known 43 Air school at Port Alfred as well as plenty of schools up country but in my view Cape Town is the best place to be.