Hello Mark,
Thank you for using the Apple Support Communities. I know having an issue with updating your iPad is not what you expect. Based on what you stated, the following steps will be helpful in resolving your issue and get your iPad updated and working again:
1. First, try restarting your iPad. If it won’t power down by holding the Sleep/Wake button until the red slider appears, try force restarting your iPad.
Restart your iPhone, iPad, or iPod touch
2. This article has some further steps to troubleshoot updating your iPad wirelessly, including how to remove and download the iOS update again:
Get help with over-the-air iOS updates
3. Lastly, try using iTunes on a computer to update your iPad using the steps in this article:
Update the iOS software on your iPhone, iPad, or iPod touch
Cheers!