Story is, my speed kept decreasing over a few days and was eventually disconnected for most of last Saturday, but was reconnected late Sunday, before BT booked an engineer.
I called BT anyway as it was clearly not right, they identified an issue at the exchange and booked an engineer for today. I didn't get any call or update after the appointment slot so I asked online what has happened and was told:
"they changed the NTE master plate and star cable at the junction box as that was old"
This makes no sense to me as I've only heard of NTE master plate and junction box in the context of within a property, which they did not attend - maybe I'm wrong?
BT Support are adamant DLM is not applied to my line however my router stats beg to differ:
Max: Upstream rate = 10705 Kbps, Downstream rate = 38772 Kbps
Bearer: 0, Upstream rate = 7200 Kbps, Downstream rate = 27399 Kbps
Stats summary
Stats recorded 23 Feb 2021 18:59:39
DSLAM type / SW version: BDCM:0xa4a1 (164.161) / v0xa4a1
Modem/router firmware: AnnexA version - A2pv6C038m.d24j
DSL mode: VDSL2 Profile 17a
Status: Showtime
Uptime: 0 hour 50 min 34 sec
Resyncs: 6 (since 21 Feb 2021 08:49:07)
Downstream Upstream
Line attenuation (dB): 22.2 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 27399 7200
SNR margin (dB): 11.9 9.0
Power (dBm): 13.1 6.1
Interleave depth: 2 2
INP: 54.00 54.00
G.INP: Enabled Enabled
Vectoring status: 5 (VECT_UNCONFIGURED)
RSCorr/RS (%): 0.0001 0.0000
RSUnCorr/RS (%): 0.0000 0.0000
ES/hour: 0.53 0
I'm starting to think they didn't do anything at all. Fault is still "open" but curious as what to do next - wait? escalate?
