Sudden drop to 20/16 from a very stable 78/16

[#1]

Just checked my connection speed and it is consitently down to 20/16. Modem is connecting fine as always at 80/30. I've tried two different routers and both give the same results. This is a long established FTTC connection that has rarely strayed from 78/16.
BTW speed test attached.
Does this look familiar to anyone? I've logged a fault ticket but no response as yet.
It's as though it has suddenly been capped at 20MB somewhere.

[#2]

Oh, from the Plusnet speed page:
Estimated line speed:
    80Mb (This may vary between 68.2Mb and 80Mb) - Checked on 2015-12-06 16:05:01
Current line speed:
    21 Mb

[#3]

needs fixing by Plusnet - live chat tomorrow should sort it
ask for their copy of the IP profile to be updated

[#4]

Many thanks Jim. Just got off chat and a disconnect/connect of the router has sorted me out.