Is there a way to purchase PPV fights on Apple tv?

Which version of Apple TV?

Where are you?

What fights?

This link - http://www.ufc.com/news/UFC-Launches-on-Apple-TV - suggests that UFC is, or at least was, available on Apple TV 3, though I cannot recall seeing it here in the UK. Apple TV 4 would need a new app rather than the Apple TV 3 channel. Other PPV providers may release apps over time.

tt2

I wasn't able to check earlier, but just to confirm there is a UFC app for Apple TV 4.

tt2