Still slow speeds even with Unlimited Fire extra. Not sure why?

[#1]

Following a change of router approx. 6 weeks ago my broadband speed dipped from mid 50'mps to a stable but consistant 43mps according to BT speedtest. Significantly lower.
Checks by BT Openreach have concluded that there is nothing wrong with my line and the DLM will slowly improve . This has not happened and im still at 43mps with IP profile at 45.78.
I have recently been upgraded to Unlimited fibre extra and according to Plusnet my estimated speed is 60mps and the line speed is 80mps.  Both bare no relationship to the speeds i am getting.

Can anyone explain this ? I thought that Unlimited fibre extra would sustain faster speeds
thanks in advance
j

[#2]

Hi jonnyfriendly,
As things haven't improved over time to due to DLM adjustments it may mean we need to intervene and report a fault with our suppliers.
Please report a fault over at http://faults.plus.net which will get the ball rolling and we'll deal with the rest for you.