Fortunately the problem was found and solved. And with that in mind I decided to upgrade my plan from 30/10Mb to 100/50Mb.
Now I'm having an issue where my speed after the upgrade seems to be on 30/50Mb. I can upload fine and it confirms that Chorus/Snap have made changes, but the download seems to be stuck at 30Mb like on my old plan.
The router I'm using is an Asus RT-N16 with Tomato Toastman. I don't think this is the issue though, as I can upload at 50Mb, so the very least I would expect is also 50Mb download if it was bottlenecked.
I've tried using a Windows PPPoE dialer (which Snap were surprised it worked) to test the connection, still the same.
I remember reading somewhere on here that some people also had issue with ISPs (maybe even Snap) not correctly provisioning the right speed?
And yes, I have contacted Snap a few times to try and diagnose this. The only thing they have really told me is that Chorus has confirm that I am in fact on the 100/50Mb plan.
Any advice would be appreciated.