Originally Posted by
phol
Call CX. Anything out of the ordinary and their website tends to bury its head in the sand. The call centre staff will do it for you in seconds.
Agreed. I've had several BA-issued CX flights from Avios redemptions, and have usually had to call up CX to get seat assignments.
The other way I've managed it is to change the FF account on the booking in BA's MMB from BAEC to my Marc Polo account, then access the booking on the Cathay site through my Marco Polo account.
As I remember it, the Cathay site wouldn't take the BA issued ticket number (starting 125.....)