Originally Posted by
Oxon Flyer
One more-or-less guaranteed route with J availability is Asiana via Seoul
Found you a J seat in ANA, B777 flights :
28/10 SYD 0930 ICN arr 1810 dep 1330+1 LHR 1730+1, MAN connections depart 1900 or 2050
8/11 LHR 2100 ICN arr 1550+1 dep 2020+1 SYD 0830+2
maybe not your top choice due to overnight stop in ICN on the outbound, but it's a J seat, on your preferred travel dates, and something to get you started.