that will always be the problem with dsl, you at the mercy of the line and if its a problem then have to deal with the openreach fault system, some isps seem better than others in dealing with these problems, plusnet seem good at line faults and they are cheap. BT on the other hand are firmly in the "if you higher than the estimated speed with no instability then no fault".
To give you more hope, you may remember on adsl I had a horrific service, as you have been a regular for a while the same time as me on these forums. the problems I had on adsl have not been present on my FTTC service, so the engineer who told me it was E-side was probably right. I am on 6db fast path.
BT Infinity 2 Since Dec 2012 -
BQM