I wouldn't buy anything from CPW.
Even if O2 were out of stock, I would rather wait than use CPW.
I got mine from cpw last July because it was the only place I could preorder the day before release, picked it up 11th July and that is the last time I have dealt with cpw, every correspondence since has been direct with O2.
It's not like the old days where all the customer service/billing etc was from cpw, now you can simply use them to buy the phone, and if you want you never have to contact them again.
You're an O2 customer at the end of the day, cpw is just sales.