Note: this is a short story, but has been included because there were not enough suitable full-length novels for 1804.
Leonard Ludgate, the slightly profligate son of a prudent and wise London haberdasher, becomes quite extravagant after he inherits his father's business. He marries Belle Perkins, who is similarly extravagant, but who also fails to understand the basic rudiments of housekeeping and budgeting. They face ruin, so Leonard agrees to become part of a confederacy of banknote forgers to pay his debts and continue to support their expensive lifestyle. Eventually, Belle becomes disfigured by using expensive but dangerous beauty products (and suffers two strokes in consequence), and Leonard is sentenced to the gallows. A moral tale indeed.

Belle is represented with a sociolect at the outset, although this gradually disappears (without any obvious code-switching). The nurse also has marked nonstandard language.
Lucy, wife of a shopkeeper, who is of lower social status than Belle, is unexpectedly nondialectal. Lucy's morals are good though (especially with regard to charity and prudence)