Originally Posted by
obduro
Not sure of the answer but is part-paying with Avios for the two tickets on the same PNR an option? This may reduce the cash component down but I'm unsure whether you could use the Joker with it. Do shoot the messenger if that's not a choice!
Unfortunately that is the same as buying WT+ and upgrading with GUF1. Actually, my experience of part-pay is that it is very expensive because you have to buy a full price ticket whereas the former option I can use the GUF1 on any kind of ticket. Btw, you can't do a two class upgrade using Avios and GUF1.