I'm trying to book Avios flights from BKK to CAN with CX in April. On the day of my travel J class on the evening flight from HKG to CAN is totally sold out in all fare buckets (Canton Fair) so although BKK-HKG-CAN is showing Avios availability, it is only in economy. Does anyone know if it is possible to make a telephone married segments Avios booking with BA into mixed classes?

When I look at availability by sector, BKK-HKG on CX is currently showing zero Avios availability throughout April in all classes, but is showing wide availability in March and May. Is it likely that seats will be made available in April?