And I believe there is a way to do something similar by using the Finnair website for your booking. I've never tried it but the details are included in the thread "Comp CX Gold (OW sapphire) with AMEX Platinum" in the BA forum. Hopefully the link below should take you to the spot in the tread where this is first discussed:
http://www.flyertalk.com/forum/briti...l#post16850181