@Linux and @Jase2985, good points.
Interestingly, the Vodafne HFC route to the Sydney server is actually quicker than the BigPipe UFB one.
tracert appears to show that a number of extra hops (?) spent bouncing around inside Spark's infrastructure before finally heading off to the US.
The US round-trip seems like such an unnecessary detour.
In any event, HFC seems about 10ms faster.
Will look into it further when I have more cycles.