Should work in GB as well, but it possibly has something to do with the
exact location that you're at. To approximate your location, your Wifi is used by OS X to scan the environment for hotspots whose location is known, utilizing a database provided by
Skyhook (as far as I know) to get that data. I would have expected for this to work even on an ethernet connection, as long as your wifi is turned on and you're in close enough proximity to a known hotspot.
Is OS X able to approximate your location when you go into System preferences->Date & Time->Time Zone ?
EDIT:
Check coverage in your area