G'day Yastiandrie,
I was informed from Telstra that there was a congestion issue, and to wait until last night to check to see if the packet loss was resolved.
I checked last night and the issue was the same, consistently with ~25% packet loss.
This afternoon I will reset the modem, and try again, but at this point Telstra back of house aren't sure what could be causing the issue, as from their end they can't see a congestion issue any more.
Thanks for your help so far.