Time to update this.
After Wombat helped me out (thanks once again)
I asked Plusnet for another engineer visit, someone from their faults team called me and we discussed the ongoing upload issue, the CS rep said that upload speeds
aren't guaranteed by BT, and that a second engineer would in all likelihood just run another pair test and conclude that the line is fit for purpose, In sending another engineer out he might get into trouble and end up incurring costs for Plusnet, so I decided not to bother.
I'm still annoyed about the issue, but there's seemingly nothing that can be done!
Why on earth are upload speeds not guaranteed in the same way downloads are?
Edited by deleted (Fri 04-Mar-16 00:07:31)