I was also able to get it sorted out after 4-5 days, after using the link provided by Traitor7402 !! THANKS! I finally unlocked the nonsense 2FA for my father in law. Still has his 350k miles thankfully.
What a mess this was, but all good now.
Link to form : britishairways.com/travel/feedbackclaims/public/en_gb/select/avi