Hi,
Unless you are on a full fare ticket or have BA/OW status you may not be able to choose seats until T-24 when OLCI opens ( and upper deck seats may be gone by then)
However ,
62AB,62JK, 64AB,64JK are the better seats on board with the window seats having almosr unlimited leg room andthe window pax can get to the aisle without stepping over the aisle pax legs.
Window seats do have the side storage bins.
64 is closer to the rear lavatory, galley and stairs.
The overhead lockers may be a bit smaller than those downstairs.
Enjoy the Upper Deck!
Regards
TBS