@licquoricewrote:I should have realised this sooner, location services are built into W10 and other operating systems. It certainly isn't using IP address for location as the location given is exact.
I wonder if you have location services turned off and your PC is using an old cached location.
You can clear location history in settings>privacy >location
I'm still not sure how GPS and wifi location are somehow transferred to Ethernet connected devices but they are. I have just fired up an Ethernet connected desktop with no wifi running Ubuntu and that picked up my exact location (a very small village) immediately.
I completely forgot about the default location in Windows 10. Have changed this to my new home address, and it appears to have helped - certainly in firefox, and in an incognito chrome window. Normal chrome windows still show my old address in Portsmouth, so not sure how to fix that!
Open Street Maps in Chrome (not incognito) now also shows a close approximation to my actual new address now too, so updating the W10 settings has definitely helped!