Well, I bought a ticket.
Paid £880. Few reasons I chose this route:
I get to fly Emirates, (tick), on the A380 (tick), and have chosen a great window seat - 46a (tick), followed by the 777 to JNB. I understand Emirates could be the only airline to have Economy on the whole of the lower deck..., consequently I a near the front, which is nice.
I return on the direct SAA flight to LHR
So, although it was £280 more than the original BA flight, I do get to fly on a couple of airlines of my choice, that I haven't done before.
Having booked online, there was a slight technical glitch, so called the Emirates 'phone number on the website, and was within approx 30 seconds talking to a very helpful lady indeed. So that impressed me. It was also nice to choose the seat, without having to pay extra (on both Emirates and SAA).
After all that, got an email today, telling me about the exciting BA sale - sods law, the price has gone down to £600 again, which it was originally, when I was procrastinating