One more thing to add: my wife has expressed a preference to fly back direct MRULGW. Will have to be a day earlier as there is no flight on Saturday. Before boarding the LGWMRU, BA did call my wife and ask if she wants this - she told them to call me (either they didn't, or I was in the air JNBMRU at the time). They are booked in Club JNBLHR, so we would only accept the same for MRULGW.

So, in short:
- BA re-books family in Club MRULGW on Friday - that's the flight they take
- BA doesn't - they fly back via JNB as planned

I will e-mail the very helpful BA agent (D####) now and request this - let's see what happens here