Once again, thanks all. 25 minutes ago I cracked it, and it now works fine. However there remains a puzzle that might interest you.
I spend 20 of that 25 typing up what I did etc., then when I posted the result got told I didn't have access to here! Somehow I'd got logged out whilst in the post drafting and preview screens and lost the lot

!
I may redo the post in a few minutes, it may be tomorrow. Probably not at all as the solution was not just to clear browsing history adn IE temporary files, but cookies and every other option as well in the IE delete page.
The interesting point is that on two machines it is working, but tracert
still gives identical routing but destination unreachable on both at Hop 9

.
C:\Users\Bob>tracert www.johnlewis.com
Tracing route to www.l.johnlewis.com [193.35.254.79]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms 192.168.11.1
2 24 ms 32 ms 27 ms lo0-central10.ptn-ag04.plus.net [195.166.128.193]
3 25 ms 21 ms 21 ms link5-central10.ptn-gw01.plus.net [84.93.248.232]
4 21 ms 21 ms 21 ms xe-10-1-0.ptw-cr01.plus.net [212.159.1.44]
5 21 ms 22 ms 22 ms pc3.gr10.telon.uk.easynet.net [195.66.224.43]
6 21 ms 21 ms 21 ms te2-0-0-111.er101.telon.uk.easynet.net [87.86.69.129]
7 25 ms 27 ms 25 ms ge1-0-0.ar101.enrdn.uk.easynet.net [87.86.73.185]
8 25 ms 24 ms 23 ms 82-111-72-42.easynet.co.uk [82.111.72.42]
9 ip-217-204-47-84.easynet.co.uk [217.204.47.84] reports: Destination net unreachable.
Trace complete.
My broadband basic info/help site - www.robertos.me.uk |
Domains,website and mail hosting - Tsohost.
Connection - Plusnet UnLim Fibre (FTTC). Sync ~ 54.0/14.9Mbps @ 600m. -
BQM
"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
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Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.