I think the previous reports were also inbound into London. So my suspicion is that some ground agent somewhere is selling the data to FlightClaim. As I said at the time, this company is based in Singapore but does have a privacy policy so I would suggest you contact them to find out what information they have on you and where it came from. I imagine BA would also like to know the answer to that one.

There is also the possibility that when you sign up to an airport's wifi they may ask - or work out - your flight details.