We regularly fly to SA and almost always choose Virgin and pay the extra to go Premium which comes in around £1200 each. If it were significantly different I would look around elsewhere. Sometimes it's nice to book a year ahead and know you've got it even if you lose a few quid on the way. The car hire back in Feb last year for a month was £600 but after Brexit went up to £836 so should have seen that one coming.
I'm conscious of any delay and wouldn't favour a stop-off somewhere else so interested how you found it. Part of me wants to see somewhere else as you have done, another part of me wants to stop-over a few days, and the third part thinks it's a few days off the whole trip. Decisions, decisions...