As long as it is right hand drive, it is legal.
You will still import taxes, duties and VAT plus the cost of shipping not worth it unless you are getting something rare or special. I have a few friends who came back from the UK and it was not worth the cost to bring their cars with them.
You cannot import a LHD vehicle into SA and register it for road use, not allowed. You'll only be able to use it on private property like a race track etc.