I currently use Flixster on my iPad and the WP8 App is lacking many of the features in the iOS App...I don't see any 'download' feature at all.
...I deleted the App till it gets updated.
UPDATE: I also searched for a VuDu App (VuDu is Ultraviolet compatible...well sort of anyways) and I don't see a VuDu App either.
I'm not sure if there is currently any way to play your UV movies on WP8 currently and the horrible mess that is UV is better documented on other forums