Thanks everyone for their advice and words of caution.

My next move is to send the paper ticket to AA in Sydney. That will be telling, I think.

There's every chance I won't take the trip at all; the reason for booking it all before the end of May 2008 was to take advantage of the 20 segment rule. Right now, at least, it's not costing me anything to make these changes - except, maybe, the whole trip!!