A question about additional YQ charges when using Avios to upgrade from Premium Economy to Club World: I want to upgrade only the return leg of an LHR to USA round trip.
Is there any difference in the additional YQ fee if I do this as (a) a single round-trip booking (using Avios to upgrade the return leg only) or (b) as two separate single bookings (using Avios to upgrade only the second of these bookings)?