Alway good to have a second option ...
Tuesday afternoon (9th) - couldn't get back onto a foreign site to complete a visa application I'd started earlier in the day. Web site gone unobtainable / down.
(House is on BT Internet in Central Scotland; router is not a BT jobby )
Could see foreign site OK through 3G via my mobe. Ergo - routing fail by BT ?
Changed my (non-BT) router to use other DNS services:
Prim'y DNS: ... 22.214.171.124 ... ... ... ... ... Google
Secondary: ... 208.267.222.222 ... OpenDNS
Success! Didn't even have to tinker with PC's Network settings.
Icon: Didn't fancy BT parentally controlling my connection, therefore non-BT router
Also, when I swapped to non-BT router, my download speed increased by 30% = Win + Win!
Probably won't bother to revert ...