If you don't download a film on the iPad from the official iTunes store, then the other way to get a film on the iPad is:
Download film on PC > convert to mp4 file (.mov usually) > open iTunes software on PC > import the file > then plug iPad into the PC > when iPad pops up in iTunes copy the film to the iPad.
Sadly you have to use the iTunes software, you can't just drag and drop like you can with a flash drive.
If you install the BBC iPlayer app on the iPad you can watch a few movies on that, but you can't download them to keep.
Of course there's also Lovefilm for watching films but again you can't download them to keep.
There are a few free videos/tv episodes to download from iTunes if you can be bothered to look for them.