Upgrading with Avios After Booking
I want to fly YYZ-LHR-ZRH-LHR-YYZ and upgrade from WT+/WT to CW/CE. I need to fly ZRH-LHR and LHR-YYZ the next day but there are no CW award seats left on my ZRH-LHR date. If I use the online booking feature it says "no availability." However, I don't mind flying ET on the ZRH-LHR sector. Can I book a WT+/CE YYZ-LHR-ZRH-LHR-YYZ ticket and then upgrade with avios online after? Is this generally reliable? I don't want to lose the award seats by having to call in and wait on the phone.
Bonus question (it's stupid, I know!) - I need to call Executive Club to do an MFU over the phone, correct? I can't call the regular BA line?
Thanks!