It is certainly possible to be in a position where you have the choice of jurisdiction, and if this is so, the choice can matter quite a lot.
I''m sure there are certain '' marriages '' which wouldn''t be recognised by the English courts, e.g. if the '' marriage '' was made in a banana republic with no bananas, or if it was polygamous, or anything like that.
If the marriage never existed, then by definition there would no marriage to annul. But I''d have thought it was almost certain that the English Courts would recognise a marriage consummated in SA.
Similarly the likelihood is that an English decree would be recognised in SA but the only way of confirming it would be a lawyer qualified to practise there.