I have to admit, I never even realised BT did a mobile service. I know they used to be BT Cellnet, which then changed to O2, but I didn't know they did one of their own again. I've been with O2 since it was BT Cellnet, and I have a very good deal with them, but BT Mobile could almost match it. My only issue with O2 is my signal quality at home, which is quite poor, but I don't know if any others would be any better, and I wouldn't want to get locked into a long contract, only to find I'm no better, or even worse off, signal wise.