Wow this is a long thread!
Just to say that Shaun our escalation manager is and has been dealing with this fault. It's escalated within BT and our thread with BT is long, but not quite as long as this forum thread! Shaun has been adding notes to the control page regarding his communications with BT.
The service has quite good sync (+65Mb/s), but often looses sync and drops the connection and reconnects a minute or so afterwards. Some days are fine but most days see either a couple or up to 20 or so drops throughout the day.
The line requires dig work in order to be fixed, and oddly the dig work was originally scheduled for 2015 but didn't seem to have happened then! -this was before the line was with us.
Shaun is chasing and chasing and chasing and doing his best. We will get this fixed!