Is it possible to get a upper reward seat outbound and a premium economy reward inbound, and then pay to upgrade to upper inbound. If so Is this likely to be an expensive fare class? Just trying to figure out if its worth us boosting our miles on an upcoming trip before the' extra booster miles' ends.
Nope, you can only upgrade a reward seat with miles, the only possible exception being at the airport where if availability remains they may allow you to upgrade with cash.
Could always buy the miles though?
Or look into booking a Combi fare