As you chaps called, they haven't reset anything.
I'm attaching a transcript here, if anyone fancies a giggle.
I genuinely can't decide if these people have no clue, or if they're deliberately being obtuse.
Either way, I'll let them know I intend to pursue a formal complaint with regard to customer service; Never mind actual service.
The last time I got to this stage, my line magically fixed itself within about 24 hours.
www.steenaudio.com/shared/TT.doc - Brown text is me.
I should also say that my nice new router tells me that interleaving is off and the delay on the line is 0,
so either someone is tinkering of their info is not accurate.
The router did previously report interleaving as being on so I'm fairly confident
it's telling the truth.