It seems that when I gave payment details, the correct priority ticketing queue was not used.

Two hours after my call today, all is ticketed (although BA.com won't give me a receipt, Finnair will give me ticket numbers and the BA App shows the same).

Thanks, Anonba. I didn't have the 'priority queue' discussion with the agent who took my payment details, evidently I should have, but I must say I feel uncomfortable telling the professionals how to do their jobs. Lesson learned.