International mobile data charges

I've just returned from France where my partner and I used our mobile phones to access emails, internet sites etc. We were both mindful of data download limits etc..... We returned to the UK on the Brittany Ferries link between Roscoff and Plymouth. On reaching our cabin we found we had no service on our mobile phones........no worries, it was a night crossing and so we'd be asleep. Shortly after departing Roscoff we noticed we'd picked up a new network and presumed correctly that it was the ship's network. No 3G was indicated and as we couldn't access the internet and we were going to sleep we thought nothing more of it. When we awoke early the next morning we both noticed that we had received messages stating that we'd incurred tens of pounds worth of data charges, which alarmed us. The following day we both rang our provider, 3, querying why we'd incurred charges as we'd both just started new billing periods and both could see we'd not exceeded our data download limits (in any case mine is unlimited). The 3 personnel we both spoke to had to go and check what had caused the charges as they were surprised. It turns out that when on a ferry crossing and once out of range of land based mobile networks we were connected to the ship's network and because we were in international waters the rules regarding data roaming in Europe no longer apply. Consequently all receiving of SMS texts and presumably automatic downloading of emails etc. and any other polling that the phones were doing, uses the ships connection to a maritime network and data charges are immediately incurred. We both complained to 3 that this is not made obvious by them, even if it is buried in the fine print of their contracts, nor do they give any advice on this if you ring them about international data roaming. As a result of our protestations they have agreed to refund all the charges that we incurred. The lesson is, turn off your phone when onboard ferries between countries where you not unreasonably presume international data roaming rules to apply i.e. to be free of charge.:mad: