We know that mid-haul A321 planes only have two classes of service, and you need to be booked in a Y/B/H fare class to UUA to the next cabin. This is more prohibitive than WT+, where you can upgrade from any booking class.

For an upcoming NYC-LHR-BEY trip, the booking class on BA.com for the mid-haul flights was K, and thus ineligible for upgrading.

I called up BAEC, and they were able to 'override the fare rules' within the system, and put me in T class for the two mid-hauls. I was therefore able to UUA on both mid-haul flights from the cheapest WT fare, much to my surprise and satisfaction! Oh - and no phone booking fee either.

Has anyone else seen similar results?