Your Apple username and password. Did you try your apple ID and password you would use for iTunes? To see if that works? And additionally I am confused as to the fact that an iPhone 5 would have such an issue. Did you check your wifi itself to see if there are any settings for this kind of Hardware? An iPhone 5 should not have these issues. I have never heard of anyone else having these problems. Screenshots would be helpful as Dah+Veed said.
I will post some screen shots later.
I have tried the iTunes username and password but it does not accept these.
It is apparently a well known problem in the UK and Apple are also aware of it although they aren't doing much about it - apparently there is to be a 'fix' in the next update? Not sure, in the meantime, I've been unable to connect to my home broadband for 4months!
As I said, none of my other devices, iPod Touch/MacBook/iPad, have this problem. Just the iPhone 5.
Thank you for your comments so far...screen shots to follow later.