Speed Halved Since Taking Out Fibre

[#1]

hoping someone could explain why my download speed has been cut in half since the installation. Ive run the BT test I found on the website which states my service is running poorly (results below) When the service first went live I was showing 40mbps but now its only 20mbps

Results Image not loaded
1. Best Effort Test:  -provides background information.

Download Speed
57.51 Mbps
 
0 Mbps 61.04 Mbps
Max Achievable Speed

Download speedachieved during the test was - 57.51 Mbps
For your connection, the acceptable range of speedsis  40 Mbps-61.04 Mbps .
Additional Information:
IP Profile for your line is - 61.04 Mbps
2. Upstream Test:  -provides background information.

Upload Speed
3.37 Mbps
0 Mbps 20 Mbps
Max Achievable Speed

Upload speed achieved during the test was - 3.37Mbps
Additional Information:
Upstream Rate IP profile on your line is - 20 Mbps

Your service was found to be performing poorly.
Please raise a fault with your service provider, stating that the BT Performance Tester tool indicates poor service throughput performance after the third test.

Please visit the FAQ if you are unable to understand the test results.

[#2]

Sorry, I'm slightly confused here:
Download speedachieved during the test was - 57.51 Mbps
You're getting over 57Mbps download, you should actually only get 40Mbps maximum. Where are you seeing 20Mbps from?

[#3]

Upload speed achieved during the test was - 3.37Mbps
Additional Information:
Upstream Rate IP profile on your line is - 20 Mbps

[#4]

ran various speedcheckers and they have all come back around 20mbps, day one was 40mbps

[#5]

looks like it has been sorted after phoning although I did seem to get cut off from the person I was speaking with so was unable to find out what the cause was without hanging on again for 15 minutes