Well inside daylight hours, turn your modem/router off for 5-10 minutes. Then on again and post the full router stats. Please also post the contents of the download and upload text boxes of the Further diagnostics. (It's easier to copy and paste them individually than to mess around with images).
Things have changed slightly this morning, so here we go............
1. BEFORE Reset:
/usr/sbin/adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 0
Channel: FAST, Upstream rate = 446 Kbps, Downstream rate = 5312 Kbps
Link Power State: L0
Mode: ADSL2+
Channel: Fast
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 6.2 18.0
Attn(dB): 53.5 33.4
Pwr(dBm): 0.0 12.8
Max(Kbps): 4812 800
Rate (Kbps): 5312 446
2. AFTER :
/usr/sbin/adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 0
Channel: FAST, Upstream rate = 446 Kbps, Downstream rate = 5388 Kbps
Link Power State: L0
Mode: ADSL2+
Channel: Fast
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 7.7 18.3
Attn(dB): 54.0 33.5
Pwr(dBm): 0.0 12.8
Max(Kbps): 5272 856
Rate (Kbps): 5388 446
3. BTW Diagnostics :
Download speedachieved during the test was - 4.92 Mbps
For your connection, the acceptable range of speeds is 1.2 Mbps-4 Mbps.
IP Profile for your line is - 4.14 Mbps
Upload speed achieved during the test was - 0.31Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.45 Mbps
Clearly the 4.92 is not accurate as it is 91% of the sync speed and not achievable in the real world at my end of the line.
IP profile still showing 4.14 though !
Plusnet have responded saying, unbelievably, we are only first line support and can do no more and I must raise the problem as a fault !! Then a further reply asked for speedtest results so I sent them a clip of my TBB tests since the issue started on April 11th.