My iPhone seems to be working perfectly since I updated to 6.0.1 and disabled the "automatic" in the carrier settings. I have never had so many signal bars on my phone since I did that. I can't understand why apple doesn't fix this bug as from what I've seen on the net since googling the problem I'm not the only one. Maybe it's just a coincidence but the update seems to have corrected the error -1 on iTunes and turning the carrier settings from automatic to off seems to have stopped the searching and no service problem. I will keep you up to date if it happens again.
Ps for some reason I can't post comments on blogger with safari on the iPhone. In reply to the comment/question below...you can't actually change the carrier settings on your iPhone if you're stuck in "no service" unfortunately. You have to keep trying until you get your carrier logo working then go to settings and the carrier should be just under Bluetooth in the settings