Not slow speed....NO SPEED!!!

I am in the PO13 area of Gosport, Hampshire. Got an email a few weeks ago saying there will be some maintenance work and the broadband service will be affected.
Since this work, our internet has been terrible, making the old days of dialup seem like lightening speed.
I am lucky if i get anything over 1Mb/s.  Usually the webpages time out, its taking so long to download. It frequently cuts off or i'm not getting any connection at all. Forget trying to watch anything on Youtube without any sort of interruption.
I am paying for 350Mb/s.

I have rebooted the Hub3, checked all connections, rebooted my PC etc etc but the broadband connection is awful. It all seems to have originated after this maintenance went ahead. Before, i had a decent connection off peak times and acceptable speed ( 100Mb/s plus) during peak.
I've attached a snapshot taken from the VM broadband speed checker.

Can anyone look into this please? I am a long time VM broadband customer and i am seriously considering binning VM and going with someone else.

Many thanks,

Simon