For some months Amazon has been informing me that "seller does not ship to Belgium" when I used the site with my Nexus 7 tablet. Oh. Ok. I don't really care so I ignored it. More recently it has been telling me "seller does not ship to the Netherlands" and today "seller does not ship to the US".
I have checked my IP address using various websites. Mostly it comes up as various UK cities. Two reported an entirely different IP address and said I was in Turkey. Both of those reported information about a Google proxy which was a clue.
Today the BBC web site has refused to allow my wife to participate in a survey as she is "outside the UK". Well it's a wet Sunday afternoon so it's time to investigate. And the answer is... data compression on Chrome under Android. Turn it on and the BBC says "go away", turn it off and the BBC allows me to vote.
So, if you encounter this problem, now you know. I assume that some geo-location services are smarter than others, can see past the Google stuff and place me in the UK. Others are a bit dim.