Line now connected, and appears to be going through plusnet, and seemingly with a static IP (although that option wasn't selected at signup).
Sync speed on the line has dropped from 2.2 to 1.92, but as long as it remains stable that is the key thing, SNR remains at 7. Long line, over the Mendips where it is foggy and damp this morning, so that may well affect things.
C:\Users\matth>tracert 80.229.yyy.xxx
Tracing route to origincxxxxx.pndsl.co.uk [80.229.yyy.xxx]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms 192.168.100.254
2 * * * Request timed out.
3 9 ms 9 ms 11 ms be443.pr3.hobir.isp.sky.com [2.120.10.36]
4 9 ms 8 ms 8 ms 195.66.224.185
5 10 ms 18 ms 7 ms 213.121.193.206
6 8 ms 8 ms 8 ms be11.psb-ir01.plusnet.bt.net [195.99.125.135]
7 8 ms 8 ms 8 ms 195.166.129.208
8 8 ms 9 ms 8 ms 411.ae0.central10.pcn-bng03.plus.net [84.93.253.82]
9 * * * Request timed out.
10 * * * Request timed out.
11 * * ^C
Still no sign of the router they were meant to supply, so not ideal for "first time broadband users".