Needed an aisle seat for left leg condition but was given same middle seat in row of 4 but further back in plane and wrong side of aisle when checking in luggage. Cabin staff did all they could but fairly full plane. Plenty of single people with empty seats beside them in window seats row. Seat allocation section could be more mindful of putting couples in the window seats and singles to fill wherever. We arrived at airport a number of hours earlier so as to arrange aisle seat on starboard side of plane but we're unsuccessful.