I have recently bought 5 iPhones for my company and I jailbroke them to use with Vodafone instead of o2.

I am afraid that my users will (even though I keep telling them not to) accidentally upgrade to 3.1 and break the jailbreak and unlock.

I know if they do this the phone won't be bricked, it'll just only work with o2 SIM and probably never be unlockable (is this true?)

My 2 questions are:

1) If they did this would a future redsn0w (or similar) and ultrasn0w be able to unlock this iPhone if the new baseband gets hacked?

2) If I decide to just give in and revert the phones to apple-fresh 3.1 and use o2, do I have to use itunes and restore up from 3.0.1 to 3.1 (official apple .ipsw rather than upgrade which I heard may lose 300-500MB of 'other' space on the iPhone. see point 1 here