Originally Posted by smashmouth
assuming you're going for BA miles availability, don't forget you can add a domestic connection if reward space is available on both BA and the connecting AA flight... so you could go LHR-BA-IAH-AA-MIA-BA-LHR on a BA miles transaction... have a play around and see if there is any US airport that has BA redemption space for your class and then see if there is an AA onward connection from there to Miami...
that's OK, as long as you are aware that you surrender the flexible nature of the ticket - i.e. add on an AA segment and your ticket becomes non-changeable, non-refundable (whereas a BA reward ticket is refundable up until the point of departure). Possibly worth paying $ for an AA connecting sector if flexibility/refundability is important.