I sold my XK140 years ago, but I seem to remember that in the book "The Jaguar XK" by Paul Skilleter, there is mentioned a technique for repair of the lower door hinge by cutting a fairly hidden hole to make the repair, then putting a commonly-available rubber plug in the hole after the repair is done. Otherwise, it is a major dismantling job.
Perhaps someone has the book & can post the information from it; otherwise, you might want to get a copy of the book yourself.
Good luck!