Be very careful not to split your travel companion on to a separate booking if their BAEC/oneworld status is different to your own: you may find it nearly impossible to get seats next to each other. Golds/Emeralds can ring up BA to get seats together under the TCP provision, a somewhat clunky and manual process. But otherwise if on 2 PNRs and one passenger has no status, you may well want to pay for a seat early on, if you want to sit together.
We noticed this on a recent flight. Not only can the lowly blue not see any decent seats, but the gold can't see any seats near the back.
Add the seat blocking of B/E and the chances of adjacent seats is further removed.
Tactic: Gold to book A on a row where F is also currently free. Blue books E at T-24 on the same row (B being blocked). On boarding ask the random that has booked F if they would be more comfortable in A next to an empty seat than in F on the same row (that would be next to the blue).