Fibre Speedtest Slower than IP Profile

[#1]

I had an engineer visit on Saturday to fix the shoddy fibre installation carried out about a Kelly Engineer (no faceplate / complete mess at the Cabinet).
The BT engineer was very thorough and I am pretty satisfied that all physical issues have now been solved.
Since then my IP Profile at the BT end is as follows:
Additional Information:
IP Profile for your line is - 54.25 Mbps
This is what I would expect given my estimate.
But the download speed has always been around 40 mbps. This is a typical result:
Download speed achieved during the test was - 41.05 Mbps
I have tried at different times of the day and early night (always wired). (I get similar results from TBB / Speedtest.net)
Is there a reason why my download test results are that much lower than the IP Profile (Is this just the way things work?)
If anyone has any suggestions, that would be great.
Thanks,
Sunil Joshi

PS.
My plusnet linespeed is 78 (since it was reset) and has not as yet come into line with the BT IP Profile.

[#2]

Hi Sunil,
You should be seeing higher results than you're reporting. Could you try a PPPoE connection and see if there's any difference?

[#3]

I will try this tonight and let you know.

[#4]

Thanks Chris, it turns out it is an internal network problem - which I'm getting sorted out.
Thanks,
Sunil

[#5]

Hi Sunil,
Thanks for letting us know. Could it be an issue that another customer might see in the future, if so could you explain how it was fixed?

[#6]

Alas, it was my fault for assuming that powerline 500 products would be sufficient to match the internet connection. It appears that the improvements to my connection have now exceeded the capacity of my powerline connection.
I have arranged to have a data extension kit installed. I had wanted it to be installed in the first instance but the Kelly Communications Engineer proved difficult.
Thanks,
Sunil