Here's the code from the QF agent at the QC. I hit the same lady in BNE yesterday on my way home as on my way out and she said she had spent an hour or more with her supervisors working this out following my request.

So, in answer to my original question (and defintely to that one only as it appears that Sabre etc is a different format, thanks for the link Globaliser), here's the code the QF computer likes for changing one sector to an AA number:

"SRFQTVQFHK/-AA#######/S#/P#"

She made a note that you must sector and pax relate.

Hope this is useful to some, it sure will be for me.