Pam as far as I know you loose it, I am not sure how it can be re-instated, but you are supposed to apply for retention of your SA citizenship first. You will never loose your right to return to SA and live there cause you were born there.
Give SA house a ring to see what can be done about your SA passport. And let us know cause there are a few people who have done this, get their UK first.
The more that you read,
the more things you will know.
The more that you learn, the more places you'll go. Dr. Seuss
"Be who you are and say what you feel,
because those who mind don't matter
and those who matter don't mind."