You could always rent out of iTunes.
In iTunes, go to Movies. Scroll down, and youll find the 'movies to rent' section. When you click on a movie, ensure you select the 'Rent' button. The downloaded movies will go in to your default 'Videos' app.
In the Video app, click on 'Rentals'. You have 30 days to watch the movie before it deletes - however, once you start a movie, you have 48 hours left to watch it.
You don't have to delete the movie - its done automatically. However, if you're running out of MB space, you can force it to delete earlier by holding down in the Vid until you get the 'x' to erase.