You actually get two DLMs dealing with your line, but both are far better than the 20CN one.
The one controlling your line is the Openreach one running on the cabinet DSLAM. SIN 498 says:-
Dynamic Line Management (DLM) is employed in GEA-FTTC. DLM constantly manages lines to maintain a target link quality (speed and stability). It does this for as long as the product exists.
At provision, the line is put on “wide open” VDSL2 line profiles allowing the upstream and downstream line speeds to run at the upper limit of the product option selected.
On the first day of operation, DLM will intervene if severe instability is detected. Otherwise, DLM will wait until the day after provision before deciding if it must intervene, provided that the line has been trained up for at least 15 minutes during the preceding day.
Sitting behind that on non LLU broadband is part of the WBC (21CN) BT Wholesale one. It sets the IP Profile but doesn't appear to do much else.
The IP Profile on FTTC is 0.9679 of the sync speed and normally adjusts immediately on change of sync. If you run a BT Wholesale Performance Test and continue to the Further Diagnostics
from the initial results page, you see the IP Profile. Divide that by 0.9679 or multiply by 1.033 and you get your approximate sync speed.
My broadband basic info/help site - www.robertos.me.uk
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Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 56.6/14.1Mbps @ 600m. - BQM
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