Slow download speeds

[#1]

After switching from BT infinity my download speeds plummeted.
My current line speed is 78Mb same with IP profile. Speed tests show around that speed as well.
But downloading through Steam, NNTP, FTP, P2P  gives me at most 24Mb/s.
While with BT I could pretty much guarantee ~70Mb/s
Does Plusnet prioritise speed test traffic and slow everything else?

[#2]

By george, I thinks he's got it!!!
Try a speedtest on http://speedtest.btwholesale.com via an Ethernet connection. Once the initial result is completed please click Further Diagnostics.  Please type in your phone number and click run diagnostic test.
Do the above with shoe on head, jimmies rustled meme in seperate browser and case of decent red to hand... make that 2.
If you do all the above, then teh amazing team at Plumnet will swoop on it like an avenging dodo and resolve it forthwith.

[#3]

Think I followed your instructions. I only had my slippers to hand, hope that doesn't effect the test
Download speed (Mbps): 73.46
Acceptable range of speeds is: 61.95 - 77.43
IP profile is: 77.43
Upload speed: 15.87
Upstream IP profile: 20