Wow Olo and Zzing, thanks for taking time to go through that thoroughly fascinating and also a lot more information gleaned than my speedtests were doing..
Not sure if it helps but I do have a static ip address, paid for, so are you saying that this actually seems to "normally" give a better routing. Funny enough until three weeks ago i had same as you - un-contended beautifully consistent connection. Hence not moving.
I wonder if turning off modem could work - happy to do that - will have to do that over night i guess. For fear of reprisal from rest of household.
Strangely enough I only sent the good WinMtr result to Origin who didn't want anything and the response was "Yes we have raised this!
" - and when I asked who to she said "the supplier "
So that seems to fit in with your ideas that by seeing the routing they have identified "the hop" that is causing the problem. And I am unlucky to be routing through it.
Thanks again for all that info - so very interesting...