The song itself is in the public domain, but certain arrangements, settings, performances, and recordings may have their own protection.
The copyright holder is EMI Unart, but most uses can be licensed through Alfred.
Warner Chappell.
Twentieth Century-Fox.
Nobody will tell me
Nobody owns copyright of music written two hundred years ago. The copyright of anything published before 1923 is irrelevant as it has expired. Copyright in an unpublished work would also expire according to the laws of the country in which it was created. For comparison, in the USA, an old work previously unpublished but recently issued would have a copyright that does not expire until 2047.
The author or the director.
Nobody owns the copyright of a single word. Perhaps you mean trademark.
the coca cola company owns the copyright
Fort Knox Music Inc and Trio Music Company. The legal title is "Please Come Home for Christmas." Note that particular recordings will have additional rightsholders.
A minor owns the copyright on any works they create.
Universal.
The churchwardens
Word Music.
Rankin/Bass.
Rondor Music.
Paramount.
There are 24 different copyright-protected items by that name.