I have changed email address and despite updating my Apple ID account, it still asks for my old email address, won't accept the password and won't allow connection to iCloud. How do I fix this?

Firstly, you need to change your details with Apple, Start here, change your country if necessary and go to manage your account.

In order to change your Apple ID or password for your iCloud account on your iOS device, you need to delete the account from your iOS device first, then add it back using your updated details. (Settings > iCloud, scroll down and hit "Delete Account")

Providing you are simply updating your existing details and not changing to another account, when you delete your account, all the data that is synced with iCloud will also be deleted from the device (but not from iCloud), but will be synced back to your device when you login again.

In order to change your Apple ID or password for your iCloud account on your computer, you need to sign out of the account from your computer first, then sign back in using your updated details. (System Preferences > iCloud, click the sign out button)

In order to change your Apple ID or password for your iTunes account on your iOS device, you need to sign out from your iOS device first, then sign back in using your updated details. (Settings > store, scroll down and tap your ID)

I have the same problem, however when I try to delete my account it asks for my old email's password in order to turn off "find my iPad" and because that old account doesn't exist, it won't let me delete it. Thankss!