That's a tricky one as availability is very limited and alternatives are thin on the ground, and you should grab those inbound seats asap. I wouldn't give you a great chance of finding a January J flight; there's not even anything available last minute in Nov/Dec at the moment.

If you have an alternative use for your 241, you could actually book IB MAD-JNB-MAD (eg 1Feb-10Mar) for 170k avios and £300. That compares quite favourably to 125k avios +voucher + £1100 on BA, though you have to add the costs/hassle of getting to MAD. Middle ground would be to fly out from MAD and get a Lloyds voucher in a hurry to get a good value one-way BA redemption straight home.

Otherwise there's seats to MRU on 31Jan but that's in a higher avios band so only really an option if you want to add that to your trip.

Or you could book Nairobi or Luanda instead, and hope to change. NBO might be a reasonable routing to VicFalls if you were thinking of going there (15k FlyingBlue NBO-LVI); Luanda is less indirect but much less obvious (https://www.flyertalk.com/forum/brit...th-africa.html).