IN ADDITION, I also needed to play with the Default Gateway Interface List so that ppp0.1 was the selected default gateway, as I have another one called USB3GO, and it defaulted to the other way around, and I wasn't getting anything happening. Moving the ppp.01 to the left side (Selected Default Gateway Interfaces) and the USB3GO to the right side (Available Routed WAN Interfaces) and making sure that Selected WAN Interface was set to Plusnet/ppp0.1 and I was good to go.
Not sure what any of that last bit was about, as nobody else mentioned it, but until I did that, it didn't work for me.
My line is still in training, but it's still giving me decent speeds.

I have one question. Is there a way to disable the ADSL chipset in the billion, so it doesn't use any power? or is simply disconnecting the line putting it into a disabled state?