We did London to Perth when DDs were 8, 3.5, and 13 months.
We flew Emirates via Dubai and they were great. We had a bulkhead seat with bassinet which DD3 just about fitted in, not that she slept much as she was awake for most of the first leg to Dubai (8 hours) and enjoyed doing circuits of the plane!
Second leg Dubai to Perth DH and I were separated by 40 rows as I needed the bassinet at the bulkhead and he was back with the other two girls, so I was on my own pretty much with DD3 for 11 hours; she slept a fair bit (night time by this point) but every time they put the seat belt light on for turbulence the crew woke me up to take her out of the bassinet and put our belt on.
Take as much food as you can - she didn't get a meal as she didn't have a seat, they did have jarred food which was pure puree for 4 month olds and awful. She shared my bread roll, cheese, rice etc. They filled her bottle of milk up for her. I took crackers, fruit and similar.
Our 2 pushchairs were transited all the way through to Perth but there were plenty of buggies available at Dubai airport, and also in Perth airport to use until ours came back from baggage. DD2 is disabled and despite asking at check in for her buggy back at the gate on arrival we couldn't get it, but they did find us 2 pushchairs and brought them to us to see us through to baggage.
Hope your flight goes well, just remember it's one day out of your life and so worth it when you get there!