That doesn't seem right. If you are being charged individually then its definitely a rental from outside of picturebox, because PB is a TalkTalk boost. If you don't have it, it would just make you subscribe to the boost for a one off charge to watch the inclusive movies. Its not possible to rent an individual movie on there.
After checking PictureBox, neither of those two movies you picked are currently on there (http://www.pictureboxfilms.com/whats-on) and are only available to rent from TalkTalk.
Make sure you go to explore boosts inside of TalkTalk Player, then PictureBox. Not the movies that come straight up to rent.