Maybe everyone knows this. Maybe I am just thick. But I'd searched for how to do this before and came up dry, and then stumbled across this on iMore. So for anyone else out there who may not be aware of this:
Enjoy buying movies and TV from Google Play? Here's how to watch them on your iOS device! | iMore
Enjoy buying movies and TV from Google Play? Here's how to watch them on your iOS device! | iMore
All this requires is that you have the official YouTube app installed on your device. Once you open it up, slide out the main menu from the left, and tap the option to sign in with your Google account. Once you've done that, any YouTube preferences you have such as playlists, watch later, favorites, along with your YouTube subscriptions will all appear in front of you. As will a menu item labelled "Purchases." You may need to tap the down arrow next to your username to make it appear.
The Purchases tab will contain all of your Google Play Movies and TV content, available for you to watch within the YouTube app.