Tonight, we looked at our booking information (telling us we would be on the A330-300 for the way there and back, which we were thrilled about), and we realised you could book your seats for the way back, we managed to book the same seats just a row in front!
The Manage My Booking page allows you to request seats from the time your e-ticket is issued.
You do not book seats, you request them as changes can be made for operational reasons. They are never guaranteed until you are actually sitting in them on the aircraft