Originally Posted by
markle
From my own personal experience: seat selection is retained if you choose the seats before you lose your status. That being said, if there's an equipment change later on, you'll be re-allocated a seat and will be unable to change it without paying.
Agreed, although it's a couple of years since I lost status, so things may have changed.
I booked some upper deck 747 seats for my final BA flight, and they stuck after I lost status.