US iPhone & O2

I've had my US iPhone (still on 1.02) for a few months now, with a TurboSIM. Works fine.

Now the o2 iPhone is here in the UK, is there a way I can update everthing to the latest release, BUT as I use an o2 SIM - is there any reason I should have to unlock it (or use TSIM)?

Any other O2 sim other than the special ones that come in the iPhone box are not recognised by iPhone.