After all the issues I've had with my line/DSL, finally we seem to have achieved a stable connection. The last issue to be resolved was I removed a 20m long length of Belden UTP that was adjacent to my BT master box - This was eventually going to connect a telephone extension but I never used it as the line was so unstable that I didn't want to cloud the issue with in-house wiring affecting things.
I can't see how unconnected wiring could affect things but when I removed the cable, the next resync of the router was 300kbps higher and far, far fewer errors. Perhaps it was picking up noise from the overhead power lines (11kv I think). Anyway, up 8 days + and counting, AMAZING.
Thanks to everyone on this forum for their helpful suggestions and thanks to Kitz etc for their excellent technical info.
Regards to everyone.
Uptime: 8 days, 9:42:19
Modulation: G.992.1 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 1,920
Data Transferred (Sent/Received) [MB/GB]: 235.21 / 1.51
Output Power (Up/Down) [dBm]: 11.5 / 17.0
Line Attenuation (Up/Down) [dB]: 31.5 / 63.5
SN Margin (Up/Down) [dB]: 6.0 / 5.0
Vendor ID (Local/Remote): TMMB /
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 32,059 / 0
FEC Errors (Up/Down): 2,612 / 1,597,530
CRC Errors (Up/Down): 460 / 47,106
HEC Errors (Up/Down): 246 / 30,675