Window in J/C and aisle in Y for me - although on the wide-bodies I tend to got for an aisle in the centre section as from experience, there is much more chance the seat next to you will be empty.

Particularly where there is 4 across the middle, like on a 330 or 340 (not BA with these although I guess the 744 has 4 in the middle) as there tends to be a couple travelling together, then an empty seat, then me on the aisle ^