iCloud won't let me download some deleted iTunes TV episodes again
Delete them from iTunes, so they don't show up in your TV section. But don't delete them from iCloud. Then they should appear with a download button on the poster for it if iTunes in the cloud is enabled (you will see a cloud in iTunes). You can either click that download button, or go to purchases in the iTunes store and download it from there.   

I think what you must've done is deleted the actual file, but not deleted it from iTunes. Normally when deleting something in iTunes, it deletes from iTunes, and then asks you if you want to delete the actual file as well or not.