Well I have an AMS - Lon (Break journey by > a week) Lon-ABZ redemption all booked in U class, and MMB says that I have lounge access in both AMS and LHR T5.
I won't get access to GC via any shiny plastic, either.
Further, it is possible to book redemption bookings in X class (4,500 miles) and U class (9,000 miles single) on a domestic with differing availability, again MMB says that the more expensive Avios fare has lounge access. Is this yet another BA I.T. Bug or correct?
Are you effectively 'paying for lounge access with the extra 4,500 avios (as it is the only difference) ?
Confused