iPad2 - iCloud email incorrect

Dear all,

My iPad iCloud ID is set to an email address that no longer exists. I have no idea what the password is, and my iCloud account has no trace of this email address in the settings.

How is it possible to change the address iCloud is attempting to use to sign into iCloud on this iPad? I am happy to hard factory reset my iPad if required, however to do this it is also requiring my iCloud account password (again, using the incorrect email address).

The email address the iPad is attempting to use is no longer available, and no longer registered with Apple.

I am really stuck with this, any help to resolve greatly appreciated.