I don't know how applicable this is in South Africa, but in the U.S., sometimes you can have D.U.I.s removed from your record after a certain length of time (also, when I came to Japan to get my visa, they didn't do a criminal check, as far as I'm aware.... and I think D.U.I.s are a different sort of violation than criminal records.... I don't know. It seems like the driving record vs criminal record would be different things. In any case, here's some advice for an American case... maybe some of it will be a good starting point for you:
How Long Does A DUI Stay On A Driving Record?