Another welcome Loulou2281, albeit a belated one!, to Flyertalk and the BA Board. ^

Looks like the Upgrade Gods/Godesses have been looking on you favourably so enjoy it and befpre you know it you will become hooked on BA and your life will change forever.

The seats on cabins can move so it is worth checking daily, as well as several times a day at least in the last few days before your flight.

Cabin movement is more likely on corporate/popular (JFK/LAX etc) routes as I have found on leisure routes most folks are going on holiday so are less likely to change.