Hi there Big Mister
43 are probably the most well known school in SA but there are also fine schools at Cape Town, Port Elizabeth and George. I can't comment on the Jo'burg area as I have no experience of them.
I'm not sure what nationality you are but as a foreigner getting permission to work in SA isn't easy. Best way is by marrying someone or so it seems.
As for converting to a JAR licence having a CPL/IR issued in an ICAO state does make things easier and cheaper.
You will still need to do the 14 JAR ATPL theory subjects
The minimum training requirements for the JAR CPL are shelved and the training that you require is purely at the descretion of the training organisation.
With regard to the IR the 50 hour JAR course becomes a minimum of 15 if you hold an ICAO IR, 10 hours of which can be completed in a suitably approved simulator. This reduces the cost by about two thirds.
To unfreeze the ATPL you will need 1500 hours of which 500 must be as part of multi crew operations. Under the JARs you need to have completed a Multi Crew course before you can get type rated on a multi-crew aeroplane, the one thing I don't know is if you have a type rating for a multi crew aeroplane on your ICAO licence whether you still need to do a multi crew course.
Best wishes
GT