That's interesting! I would actually come to the opposite conclusion about most of those quotations: that is to say, that many of them could reasonably be "express" to stand for "express mail" OR "the messenger," but some definitely could not be the messenger.
For example, no sane man would entrust the details of Lydia's escape to the messenger, but rather to the letter. It would have been all over Meryton by morning, and concealment was particularly desired. Therefore the "had an express...to inform us" line would have to be referring to the letter. The line from Mrs. Hill, however, clearly delineates a difference between the express ("messenger") and the letter, so there were clearly times when "express" meant messenger. I would draw the conclusion that the term could be used in either way, but I can see that you draw a different one.
I would be curious as to what leads you to make the assertion that an express was not associated with the royal mail. Other things I've seen seem to indicate that they were. When I get back upstairs in my house I'll check my source materials but I have weak knees so I don't go up and down all the time!
For example, no sane man would entrust the details of Lydia's escape to the messenger, but rather to the letter. It would have been all over Meryton by morning, and concealment was particularly desired. Therefore the "had an express...to inform us" line would have to be referring to the letter. The line from Mrs. Hill, however, clearly delineates a difference between the express ("messenger") and the letter, so there were clearly times when "express" meant messenger. I would draw the conclusion that the term could be used in either way, but I can see that you draw a different one.
I would be curious as to what leads you to make the assertion that an express was not associated with the royal mail. Other things I've seen seem to indicate that they were. When I get back upstairs in my house I'll check my source materials but I have weak knees so I don't go up and down all the time!