Yes, it was interesting to learn that the refrigeration ships were so old. I wonder what cooling agent was used.
Anyway, I have searched through old newspapers. No SA grapes appear, just oranges and grapefruits. It seems that the grapes were English indeed, harvested between Augost and October. I find a note that grapes from royal vineyard were handed over to hospitals treating wounded airmen. English Muscat grapes were quite expensive, from about 2 to even 4 shillings.