Connect your device (iPhone/iPad) to your desktop/Laptop via a USB cable or Wi-Fi!
1. Open the iTunes app. on your Desktop Mac/Laptop Mac. (this process cannot be done from either your iPhone or iPad)
2. Look at the drop-down menu which can be found underneath the Rewind,Play,Forward controls. Beside 'Music','Films','Apps' etc in this menu, you will see a tiny ^up-down\/ arrow. The menu will have 'Music', 'Films', 'Apps' etc in the list. Use the arrows to select 'Films'. (Note:If the drop-down menu does not have 'Films' in the list, use 'Edit Menu' below the list to add it to the list, by ticking the box next to 'Films', then select 'Films' from the drop-down menu.)
3. You should now see in the main window to the right of the lists on the left, either icons representing the films you have or a list of them.
4. Select the film(s) you wish to delete by clicking only once on the icon/name on list. You should now see a highlighted (on my mac it's blue) ring around the icon you have selected.
5. On your keyboard, press the 'Delete' button once. (You may be asked to confirm the deletion. If so, accept/agree/delete.) Ensure that the film(s) you want removed from your device has been deleted from the main iTunes window on your desktop/laptop.
6. Make sure that your iPhone/iPad is connected to your desktop/laptop either by a fixed USB lead or via Wi-Fi by looking for it's little rectangular icon to the right of the drop-down menu mentioned above.
7. Sync your device and afterwards check the contents both on it's own iTunes and in your iTunes App on your Desktop/Laptop.
8. That should do it. I'm just some guy so please don't send me death threats if this doesn't work. If it does work, go out and do something nice for somebody.