Hi Swan, I've been able to use the QR website fine to allocate seats. Just enter the PNR and last name under Manage My Booking and do it there. In fact I've been able to change my Qantas and airberlin seats also through the QR website but in general each carrier's own website does it. I did my CX ones online on their website as well.
Sorry, I am missing something here where do you obtain the PNR for QR?