Welcome to FT (I see you are still relatively new).

Are you referring to this thread?
http://www.flyertalk.com/forum/briti...ht-oxygen.html

From there it would seem that any random seat assignment as long as it's an outboard row on the 777 and any seat on the 747.

As BA don't guarantee seating assignments you will have to wait till you are at the airport and receive your boarding card. I would assume that BA will try and place you together, but they do not have the requirement to as far as I'm aware