Just had a text from O2:
So I put my work phone's Vodafone SIM card in, and connected it to iTunes. After a short while, the following screen appeared:
And it activated the phone with the new SIM card inside it.
Definitely all working!
So I put my work phone's Vodafone SIM card in, and connected it to iTunes. After a short while, the following screen appeared:

And it activated the phone with the new SIM card inside it.
Definitely all working!