Thanks for the comprehensive info KPT My iPhone is only a month or so old, so I assume I'm on the latest fireware (I'll check later, my phone is currently off as I don't get reception in the office).

I was considering jailbreaking my phone anyway for other reasons, so this adds weight to the arguement to do so.

I was spanked to the tune of £120 for roaming internet on my old nokia when in the US (merely a few emails / webpages), so I'm very aware of the dangers of mobile internet abroad !!

I've no absolute need for mobile internet, or even having a phone while in Japan - I'll be on holiday, and I should (try to) detach from work for a few weeks. Besides, due to the time difference I don't want people calling me!