Not wanting to be left behind recently, I paid full fare for my tickets to Oz. A simple introduction was made, with Company ID card, not BA by the way, to the Purser/CDC on entering the aircraft each time. On all four sectors I was told to wait under the stairs. Some time later I was led to a Club seat, indeed, on one occasion to First! (It may just have helped them load another passenger into economy/coach!)
The thinking was, it seems, that having paid full fare as an airline pilot, I was very probably slightly mad and in need of some treatment, lay back, relax and drink this, type of treatment!
As for the rights and wrongs of the Purser using his discretion to upgrade pax, even if this is contrary to the letter of the FCN, I have to say that before long none of us will have any discretion to decide anything in the near future.
I say, long may it last!