I have 2 films in my iTunes Library the same, for some reason. If I delete one will the files from the other be deleted? If so is there any way I can merge them into one
It's likely you have two copies of the movie. Deleting one should not delete the other. You can confirm that by doing a Get Info > File: Location on each of the movies. They'll almost undoubtedly have a different file path.
Considered as a database, the iTunes Library is not very sophisticated. It'll locate duplicates, but It doesn't allow for merging records.
It's likely you have two copies of the movie. Deleting one should not delete the other. You can confirm that by doing a Get Info > File: Location on each of the movies. They'll almost undoubtedly have a different file path.
One of the options for getting media into iTunes is to copy. That is, leave the original alone and copy/transform into iTunes. If you can see both, and they are the exact same name Including extension), then check the size. If one is small (like less than 4K) then it's a link. But I suspect it isn't, and you can safely delete one.