As per some of my replies in between this one -

It seems (by some miracle) that BA have finally changed my dates as requested. My QF64 Flight from JNB - SYD with a next day connection to Perth on QF has now been changed to same day QF64/FJ5252 (JNB-SYD-PER) and shows up as confirmed on BA - on manage my booking on the Qantas site the flights show up as JNB-PER. My receipt has ticket numbers so I am guessing all is in order.

No change fees or any repricing was done for this change or the previous one (when I changed the date and carrier on AKL-JFK).

I guess things will go quiet until around the Dec timeframe when I will make a series of changes to add in new dates for all my US flights (all 6 of them) as well as my trip home to the UK for Christmas (Dec 2026)

P.S. I am still seeking a solution for finding out why EF shows D availability on Qantas (for instance on the Syd to Per routing) but BA cannot see it (says there is none). Regardless of PoS (which I think does not matter these days) why would this be. This would seem to be some error on BA's part as (per the above), When I got the FJ code share booked FJ codeshare showed D5 in EF and the QF actual flight number showed D7 - BA could see the FJ D availability hence my booking but none on the QF number - and there are many flights to PER from SYD but BA can see D on only one of these flights for the numerous days I checked despite EF showing wide open in D on all of them.