You should check to make sure your rows 31 & 32 aren't over the wing, which would ruin an otherwise great view. I've taken several BA 777s on the Boston-Heathrow route, including G-VIIG (twice), G-YMMC, and G-VIIU...got to sit in the cockpit enroute on all flights. Alas, that was years 1997-2000. It's a different landscape now, though. My first flight aboard G-VIIG was on the morning Boston-London flight, in late November 1997. The plane was a third-full, and I could have played football in the whole back section and not bother anyone. I staked my claim in the very last row of the plane, which afforded excellent views. I managed the same thing on a Singapore 777 from Amsterdam-Chicago last October, 9V-SVC (then their newest 777). Given that your flight is so far in advance, you should try for seats way in the back so you'll be sure of unobstructed views.
Chris in New Hampshire