Horrendously slow download speeds in evenings

[#1]

I was on standard ADSL, didn't have a need for fibre, but then with more and more devices I upgraded to the 40Mbps package, during the morning it's fine, during the day it's fine, come the evening, it's half as quick as my adsl connection was, late evening and it's fine again.  

Here is an example of my current speed http://www.thinkbroadband.com/speedtest/button/1474577135570764155.png

and BT wholesale speed test, of a similar experience last week

Some answers or investigation would be appreciated.  Oh and I'm using Plusnet's hub one, the filter that came with it, and I've used the test socket to no avail, my phone is fine etc...

Thanks 

[#2]

I've waited 3 weeks for fibre, it should of been active on 19th, no joy until 6am this morning, 36mbps! Then got home from work tonight, barely reached 3mbps! No joy from customer service. Not happy