Originally Posted by
onobond
Hypothetical question: What if OP had used the two GUFs before BA discovered they were wrongly issued. Could s/he face any economical response for the fare differences, when the fault so obviously was on BA's side?
BA giveth, and BA taketh away.
No. There are no legal grounds that would allow BA to reprice the ticket. That said, BA could grab the next GUF that appears in the account or even downgrade the reservation to the class actually paid for. I do very much doubt they would do either.