Originally Posted by
Geordie405
Your profile states that you're EXP. If that's true then you'd get free seat selection at the time of booking.
I've never had free seat selection at time of booking, but I've been able to select seats after getting my confirmation from BA.
Book through BA (or the AARP portal), don't select seats because the system will charge a fee. After you get the confirmation, click through and select seats. Then monitor them periodically, as the aircraft type can change, especially if your travel is further out.