Hi mates,
I just looked on major carriers pages, and found that currently there is NO direct London-Sydney flight

It was a major advertising feature of the airplane and airlines simply avoid it

They seem to always have a stop at Hong Kong. This makes the 9000 nm flight to be just under 23 hours ! That is horrible. It could be done at roughly 20 hours with limited pax & full tanks.
Using the plane in these conditions makes it a bit cheaper "just another 747" in the sky. I am still waiting the first brave operator to order a 800 seater version...