I've tried a that link a few times over the last couple weeks, and I just the "oops page". Assuming there's nothing that can be done online with that, so I'll put it on the list for post covid phonecall to VM call centre in the summer.
Good news thought is it was 100% my fault, wired and 5GHz WiFi are seeing full bandwidth 100-110M. My laptop strangely started to prefer the 2.4Ghz WiFi - presumably running 802.11g which totally explains it as that's the Max speed for that standard. Just thought I'd update incase anyone else see similar