Chris,
The Plusnet trouble-shooter reply said that they had done a DLM not a CLT
DLM reset performed...
New Profile: WBC 160K - 24M Medium delay (INP 1) 6dB Downstream, UC Low delay (INP 0) 6dB Upstream (ADSL2+)
Sync : 9927
WP Profile matched to sync.

I have informed Plusnet of my current status and assume they will do another line test and show me their improved results.

The current line speed is,
Estimated line speed:
There's no speed estimate currently held on your account.
Current line speed:
8.7 Mb
The Assus router will allow me to disconnect and reconnect but I wanted to move the mains transformer to a different mains socket so it was switched off and on manually which I assume was the same as doing it in the router login.
Current router connection below,
Modulation : ADSL2+
Annex Mode : Annex A/L
Line State : up
Lan Tx : 8132445
Lan Rx : 3882917
ADSL Tx : 3773228
ADSL Rx : 7752754
CRC Down : 0
CRC Up : 1653
FEC Down : 0
FEC Up : 48173
HEC Down : 23354
HEC Up : 0
SNR Up : 5.5
SNR Down : 6.0
Line Attenuation Up : 23.1
Line Attenuation Down : 44.0
Data Rate Up : 1076
Data Rate Down : 9879

I live and learn and do appreciate your kind advice.

John

In reply to a post by planman:

The Plusnet trouble-shooter reply said that they had done a DLM not a CLT
DLM reset performed...

Sloppy on Plusnet's part. They should have done a Copper Line Test first, but never mind, let's hope it all remains stable.

Considering you wanted to move the mains transformer, then your approach was quite reasonable. It's always better to power down first by the way, rather than just unplug the modem/router or filter from the line if you ever need to do that.