MichaelOLearyGenius: I was right at the back of the top deck. I deliberately do that and chose an inside (not aisle) seat and invariably get all 4 seats to my self. The guy in front had all four seats too. There are cabin up top only has 4 or 5 rows. Don't think the plane was all that busy.
Be careful with that if you plan on having a quiet flight! That small cabin on the upper deck is also where BA tend to pre-allocate group bookings. Can be party central up there.