Hey dagger and welcome to the forum
thank you, always fun when ppl reporting back good speed increasing. Most of the time ppl reporting back, when it dosent help at all or speed got even worce
Do you use any tweaks after you changed to Telestra BigPond Cable? If you use same tweak as you had with your previous ISP it might be in conflict.
Best way is to open cablenut, click delete cablenut tweaks + click save to registry and reboot.
Now check speed, and follow the tweak guide, make sure to find the right MSS value and then use one of my custom files.
Post score before and after tweaks
good luck
VanBuren