It's possible that your powerline adapters are impacting your VDSL connection (rather than your wi-fi) as they operate on the same frequencies as VDSL - some people have no obvious problems, other people are massively impacted (happened to me). Have you checked your router logs to see if the VDSL connection is dropping and/or whether you're getting a lot of errors (you should be able to get reasonable info out of your VR400 unlike if you were still using a HH).
What about a wired connection to your router? If that still works, then your broadband itself is still OK and it's probably a problem with the Powerline and/or wi-fi. If it doesn't work, there's a problem with your broadband so what do your router stats say?
Powerline is notoriously flakey (e.g. some combinations of sockets work together, others don't), and moving a plug or adding a new plug can cause it to impact your broadband connection even if it used to work fine.