Thank you, Captain, for answering those questions.

I've been looking around for more info regarding the possible reasons why Catherine Morland might not have been free to accept Henry Tilney's invitation to dance in the absence of her previously-engaged partner John Thorpe. No luck so far, but I did come across some interesting historical dance links at the Library of Congress website.

At the bottom of the page I've linked the main page from a dance manual (in facsimile form) published in 1808 (somewhat outside of the timeframe for NA) by dancing master Thomas Wilson:

An analysis of country dancing: wherein are displayed all the figures ever used in country dances, in a way so easy and familiar, that persons of the meanest capacity may in a short time acquire (without the aid of a master) a complete knowledge of that rational and polite amusement. To which are added, instructions for dancing some entire new reels; together with the rules, regulations, and complete etiquette of the ball room. By T. Wilson ... Embellished and illustrated with engravings on wood, by J. Berryman; London, Printed by W. Calvert, to be had to Mr. Dutton [etc.] 1808

The preface includes an interesting paean on the superiority of dance (over riding) as one of the two amusements "highly conducive to preserve a healthy constitution". A little later it goes on to say that dancing serves to preserve some young ladies from the dangers of novel reading and the gothic sensibility!

The section that starts here, had me laughing when I got to this part, in light of the GR:

...her evenings are ushered in with subterranean caverns and hair-breadth elopements; she forms a strict acquaintance with the manners of the Gothic age, but knows neither the vices nor the follies of the day. Thus equipped at twenty she enters the theatre of the world, to sustain a character she knows not even in theory. Innocent and unsuspecting herself, she sees no treachery in others; flattery delights her and those she considers her best friends who most praise her beauty and accomplishments; she looks in vain for the heroes she has read of in romances, till some designing fop, taking advantage of her inexperience, plays the lover with all the warmth and protestations of a Romeo, till by prayers and promises, (added by the resemblance he bears to Tancred, Selim, Edwin, or Ronaldo) she is persuaded to quit her father's roof, to become a countess of the imaginary wide domains and splendid mansion of a knight-errant. Horrible delusion; the villain flies, leaving his innocent unsuspecting victim a prey to infamy and despair.

The etiquette section comes toward the end of the manual. It refers to the Bath Guide as the best of the manuals, and goes into some of the details about sets and "breaking in" line that Captain Everett referred to in his post.