For, passing by the actual daughters of the house, she had chosen Clara
The narrator says choosing the poor Clara reveals Lady Denham’s good side. However, one questions Lady Denham’s intentions because she knows that the cousins offered hospitality in hopes of receiving something in return. Lady Denham is comically petty in snubbing the family by ignoring the actual daughters.
the politic and lucky cousins, who seemed always to have a spy on her
The narrator suggests that the cousins are keeping an eye out on the rich old lady.
as prudently as possible to defy the reputed expensiveness of such a home, and at the end of three days calling for her bill that she might judge of her state. Its amount was such as determined her on staying not another hour in the house, and she was preparing in all the anger and perturbation of her belief
Although she probably could easily foot the bill, Lady Denham’s extreme reactions to people/establishments who take her money is quite outrageous. However, it seems short-sighted of her not to pick a cheaper place to stay in general.
Though now and then, a littleness will appear. She cannot look forward quite as I would have her and takes alarm at a trifling present expense without considering what returns it will make her in a year or two.
Lady Denham is risk averse, but Mr. Parker does not seem to recognize her miserly character.
and they were older in habits than in age
This is the elegant Austen way of calling people “grandmas/grandpas” even if they are not of senior citizen status.
she remained equally useless.
The narrator is trying to say nicely that even though Mrs. Parker is a kind woman, her lack of initiative makes her a poor match for Mr. Parker. In short, the Parkers are a silly couple.
All that he understood of himself, he readily told, for he was very open-hearted; and where he might be himself in the dark, his conversation was still giving information, to such of the Heywoods as could observe.
The narrator spells out for the reader that silly Mr. Parker is a good person, but he is simply not very self aware.
What in the name of common sense is to recommend Brinshore?
Mr. Parker believes that the best way to sell his resort is by trashing competing resorts.
But had we not better try to get you—" "Our coast too full!" repeated Mr. Parker.
Mr. Heywood’s practicality is getting in the way of Mr. Parker’s fervent sales pitch, but Mr. Parker will not be stopped!
My name is Parker, Mr. Parker of Sanditon;
After having an extended interaction, Mr. Parker finally reveals his identity in a grand manner, complete with a sales pitch on his resort!
consulting his wife in the few words of "Well, my dear, I believe it will be better for us
Mr. Parker’s version of consulting his wife is simply informing her what he has already decided.
down in the weald
This is a play on words with "Weald" (described above) and "weald," which is the Old English word for forest.
I am sorry to have the appearance of contradicting you, but from the extent of the parish or some other cause you may not be aware of the fact.
Mr. Parker is so sure of himself even though he is not from the area!
There, I fancy, lies my cure—" pointing to the neat-looking end of a cottage, which was seen romantically situated among wood on a high eminence at some little distance—"Does not that promise to be the very place?"
Mr. Parker’s silly character immediately reveals itself as he passes a romantic judgement that a random cottage without any context must house a surgeon.