However, it appears that the installer reused a Cat6 Cable that was specifically wired into the garage when we built it to provide internet access out there, but was not yet connected to the modem or a hub.
I went under the house last week to connect it all up, but found something already using it:

I can only assume it is the VDSL install as I don't believe we've had anyone else under the house since the Cat6 was installed (except for the insulation, and I'm quite sure they didn't do this!). Am I correct that this would be my VDSL connection? If so, is this normal, to just hijack a cable that I've got earmarked for another purpose?
I'm going to call Telecom to ask them to come and rectify the problem, but first just wanted to ensure that this is the VDSL install, and get your thoughts on whether they should be doing this?
Many thanks,
Adam