Thanks very much for your local knowledge.
Things are coming to a head as we'll be in ZA for the first half of February and I have a couple of short Euro trips in the meantime. I think this precludes getting an alternative as there's not enough time to line everything up. I've been away and have not paid enough attention to personal dates. Silly me.
We're also looking at taking the Premier Classe train from Johannesburg to Cape Town. We've done CT-JB before and enjoyed it. However, Namibia would trump this idea in an instant!
If you thought there as a way of organising a Namibia trip without causing grief to your friends, please PM me, though with just under four weeks to go, I'm thinking we should plan ahead for a later trip to Namibia.
Many thanks for your advice!