Something very interesting happened in regards to the above phantom availability on EY website. Yesterday I checked the website again looking for LHR-SYD flights in December and again the only flight could find for the dates I need was the same EY18/EY450 as quoted above. Again, it showed 1 Guest available when searching LHR-SYD but when braking the segments: LHR-AUH 1 Guest, AUH-SYD 0 Guest.
At that point I gave up and called AA to refund an existing cancelled booking I had on that same route, pay the $US150 penalty and re-book with BA or QF.
I called the AA SYD number and don't know why but decided to ask one last time for that EY flight. The nice agent put me on hold while looking for it and eventually, as expected, came back with negative result.
At that point I said that if he can't find me a seat then I wish to refund the points and taxes from my original (cancelled) booking. The agent then asked to put me on hold again while checking with his supervisor if there is anything else available on EY before processing the refund. After about 5 minutes waiting he came back and said his supervisor was able to book the EY flight I originally asked for. Well, that was a huge surprise! Two agents before couldn't do it and someone above them managed to somehow book it even though the AUH-SYD segment was not available on EY website.
I got a new booking ref and immediately called EY to confirm and select seats. After a few hours got the e-ticket as well so it looks OK.
That AA agent was a champion for moving my request to a higher level (even though I didn't ask for it) and by doing that he saved me going back home on an inferior product and paying $US150 refund fee on top of that.
Happy days