No internet connection since around 4pm today

[#1]

I tried to keep the technical stuff to a minimum and tried to explain things in as simple a language as possible realising that you were as you say "a complete novice". If you'd like me to explain things again, perhaps "one step at a time" tell me at what point you lost the plot, and what you could follow and we'll take it from there. Understanding some of the basics is a good idea so that should you have any issue in the future you have some idea of what to watch out for.
Please do try running the BTw Performance test again. It's a facility that should work for everyone, when you do the diagnostic bit, the data is stored on a BT server that Plusnet can see and that can be vital in more complicated faults, so Plusnet must get BTw to fix it if it's not working for you.
Your current line speed being 5.5Mbps is  because your speed dropped to 6464 as noted in your reply #36 at 1529.
I expect Matthew will do that SNR Reset for you.

[#2]

Thanks - still getting the same error message when I run 'further diagnostics'. 

[#3]

Hopefully Matthew will be along to pick up the Reset and the BTw Performance Test issue

[#4]

I've put through a reset but on 20CN it can take up to 4 hours.
The performance test issue has been flagged up as well.

[#5]

Thanks a lot Matthew 

[#6]

Thanks Matthew.
should I be doing anything while the reset is going on?
Just heard from a local business up the road that their phone line is still down - I think there have been some major issues at the exchange recently. Anyway, at the moment the speed feels okay, but I would still appreciate confirmation that all is okay from you guys if that is possible.
I should clarify also , that I did the BT test with wireless connection. It's quite complicated getting the router wired up to the PC for an ether connection without losing the phone line - all in different rooms, and would mean a lot of long wires trailing all over the place... plus I haven't been able to get out of the town lately to buy new cables due to floods, so hoping not to have to go down that route.
I should also add, that the DSL cable that I was using was going across a doorway - I put a mat over it, but probably walked on it quite often - could that have caused damage to the cable? Things seemed to get better when I tried the new cable. The new one is hanging across the doorway, so I'll have to do something with it - in the end, probably buy a longer one I can thread around the door frame - or does the length of cable cause problems too? So many variables!

[#7]

When the reset happens, you will have a brief loss of sync whilst the modem/router resyncs at the new speed (all being well), the thing to look for in your stats is the change in Bandwidth Down to 8128 and the SN Margin down will be around 6dB. Post up the stats when you think it's happened.
Yes, longer standard ADSL cables will be a problem because they aren't twisted pair wiring. Twisted pair cables are available and I'll give you a link to a reliable source later if you want it. Do not be conned by ads for Hi speed modem cables with gold plated connectors rubbish. Most are not twisted pair. It's can be a minefield. I'll post back this evening.

[#8]

Here we go! 
DSL Connection 

Link Information
   

Uptime: 0 days, 7:31:43

DSL Type: G.992.1 annex A

Channel mode: Interleave

Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,244 / 9,024

Bandwidth (Up/Down) [kbps/kbps]: 448 / 8,128

Data Transferred (Sent/Received) [kB/MB]: 0.00 / 120.93

Output Power (Up/Down) [dBm]: 11.5 / 14.0

Line Attenuation (Up/Down) [dB]: 2.0 / 9.5

SN Margin (Up/Down) [dB]: 30.0 / 9.0

Vendor ID (Local/Remote): TMMB / TSTC

Loss of Framing (Local/Remote): 0 / 0

Loss of Signal (Local/Remote): 65,539 / 0

Loss of Power (Local/Remote): 0 / 0

Loss of Link (Remote): 0

Error Seconds (Local/Remote): 131,072 / 0

FEC Errors (Up/Down): 16 / 163,500

CRC Errors (Up/Down): 10 / 9,081

HEC Errors (Up/Down): 28 / 10,233


It worked, I think! 
thank so much Matthew and Anotherone!
I'll be back sometime tomorrow - out tonight ...

[#9]

That looks much better. Just check your Current Line speed it should say 7.15Mbps

[#10]

Glad to hear it's improved.

[#11]

All looks tickety-boo! 
Phone exchange :GRANGE-OVER-SANDSEstimated line speed:8Mb (Download speed could vary depending on line conditions. Estimates are the maximum speeds that your phone line can support. These speeds are dependent on the package you choose.)  - Checked on 2015-10-17 14:06:57Current line speed:7.15 Mb
Thanks for all your help - can sign off here now I reckon.

[#12]

Enjoy your connection