DJC wrote:

I use mobile broadband for my internet connection. I don't have a
smartphone, just a PC. I sometimes, but not often, log into Google; I
have location etc, disabled. Generally Google thinks my location is
London, sometimes maps etc seem to think I am elsewhere, but not
Somerset which is where I am.

Google's geolocation on a PC, and their geolocation on a phone are like
night and day, the phone has numerous radios (gps, wifi, bluetooth, 3G)
to locate you by, and the whole "fleet" of phones effectively act
together to give pretty good results.

e.g. even if your phone has GPS turned off, someone else's phone is
likely to have visited the same location with GPS enabled and reported
what wifi access points are visible from there, so your phone reports
what wifi it can see, and how strong their signals are, then google can
generally work out where you are quite reliably.

Their location on my PC wanders wildly around the country, and I like
that I'm not in their cross-hairs.