I didn't install 8.1on my new iPhone 5c as it was too buggy. It downloaded automatically when my phone connected to the web for the first time via WiFi. So it sat on my iPhone taking up 3 gig of space. There was an option under Settings, General, Software Update or Usage that offered me the option to delete the update. I was waiting for more information to see if it was safe to install or if I should delete it. This option seems to have disappeared now that the new version 8.1.1 is available to download.