Not sure what's going on here over the past 48 hours or so, VDSL has been pretty faultless since installed a couple of years ago.  Normal speeds have been about 45/8.5.
For peter reader's benefit, yes I've reset router, it's connected via ethernet, there's nothing else downloading (I've turned wifi off), router settings haven't been touched, Chorus set the VDSL up with master splitter.  I shifted the access point, but that's been fine for over a year.

It has been dropping to below 1Mb/s and very choppy, Netflix etc basically unwatchable.  I think the SNR and attenuation figures are the same as they've always been.  It's possible that someone's dug up or damaged cables in the area, shifting holes in the ground from one place to another has been pretty common in the area we live since the Chch quakes, but I'd have thought that if that was the case, I'd have seen that in router stats below.

Sometimes if I try to access router settings via web interface, it's very slow to connect - as if the router isn't responding.

I don't have a spare VDSL router around to try.  I'd been thinking about buying one, but fibre is only a few months away, I'll switch to that as soon as possible.

As I was about to post, I thought I'd run speedtest again:

That's back to normal.  I hate intermittent issues.  I'll post this anyway as I'm guessing the problem will return.