I second that!
Im hoping that i can put in my contract O2 SIM in (that doesnt run out till Feb 2009) and then just add an unlimited data to it. BUT i do have a feeling that to stop any hacking they are going to tie the PAYG SIM that comes with the phone to the phone...also i suppose they'll know how much you top up so if you swap out the original SIM they'll know about it! Maybe a way to get around that is to put say £10-£20 on the PAYG SIM, swap it out to an O2 contract SIM, then if they ask you can argue that never really use the talk time or texts?
Thoughts??
if im not mistaken, you'll have make a charged call every 180 days to keep the sim active. but apart from that, your plan seems fine.