Interesting Visvanath,
Most of the search results mention accessing Moodle itself through 127.0.0.1 but in fact this is the db connection. I'm already accessing Moodle via a statically allocated IP on the home router to be consistent rather than relying on the one allocated by the DHCP server part of the router. My c:\windows\system32\drivers\etc\hosts file already has an entry to map 'localhost' to '127.0.0.1' which worked fine until Windows 10 and it still has that mapping. That is what is odd about this. No amount of temporally disabling the firewall etc. solves the problem, bar specifying the IP.
Cheers,
Gareth