I realize I am shouting into the void, but I do find the YQ prices frustrating with UUA situations too. Yesterday I upgraded a 3-segment itinerary from WT+ to CW and it cost $750/person extra in addition to the Avios portion. As part of the same trip, I upgraded EY AUH-LHR from [cheap] Economy to Business with GuestMiles and no cash surcharge was needed.