Hi, I am considering changing the class of an all-miles award ticket, booked using a UK BAPP Amex 2-for-1, from WT+ to CW/F. I've paid 75k for 2xWT+.

2 seats of CW availability have opened up, would I have to pay the full difference in price, or would the 2-for-1 still count, as if I had booked the tickets in CW originally?

Thanks