Q: Error message about not enough storage in iCloud for back up has totally locked my iPad. Option of cancel will not work?

After doing system update and setting up iCloud overnight an error message has appeared stating my iCloud does not have enough storage space for a backup. This error message is effectively locking my iPad. The cancel option does not work. I can activate any option elsewhere on the screen, I cannot even turn it off. The error message other option is settings. It would go to settings but once again I could not do anything on that screen either. Double tapping home button has let me close apps etc but now I can not even get into settings. Help please!