I have stated in the ticket that I will not accept charges for the above reason.
You wont get an engineer then, sorry. We identified a fault on your line, but have no idea where it lies - your equipment, internal or external wiring or exchange equipment. You do our tests, we take your word on the basis that you accept charges if you havent bothered to do the tests, or didnt do them properly and the engineer subsequently proves that something of your responsibility is to blame. This is your fundamental misunderstanding of the situation. As I (and numerous other Plusnet staff) have advised, do the checks and you have no risk of charges.
Out of interest, can you also explain why BT would recommend ceasing a connection that, whilst not perfect, does actually connect?
Because the line is too long to sustain a workable service, nevermind whether it connects sometimes or not.
To me, that doesnt make any financial/business sense whatsoever on PlusNets part.
The profit margin on your account is tiny, as soon as support staff get involved then were in the red. With the number of times your faults ticket has been touched, well never make any profit from you.