Are you looking for a sex, crime, and murder mystery set in Regency England? I'm afraid you haven't found it. All that dates the book's story is the mention of 1819 at the beginning of the first chapter. After that, it just is a generic sex and crime story. Stone Devil Duke by K. J. Jackson is showing up major defects in writing without doing at least some minimal research.
Who would ever want to go to Dijon? This question and variants thereof is the most asked in this book. But it all starts in London with a kidnapping gone wrong. Flight and chase take the reader through France to Paris and from there to Dijon. No car races and police investigation, I'm afraid, the year is 1780.
Dive into Paris and Versailles during the time of King Louis XV. Corruption and intrigue are ripe. France is an open playing field for the Duke of Avon. the English peer has earned the nickname Satanas from his enemies. Broke as a young man, he had toured Europe as a gamester. He gambled a young Austrian noble out of his fortune and retired to enjoy a lavish and sumptuous lifestyle.
The English and the French are well known for their long lasting friendship built on mutual esteem, or maybe not. The Entente Cordiale is but a thin veneer over the gulf that separates the two countries. But indeed, there is a lot of fun to be got out of a situation playing the French against the English.
Pan Books published The Forgotten Garden by Kate Morton. In it, she tells the stories of three women in search of their roots covering a hundred years of family history. While two of them were displaced by no choice of their own, the third is set upon her quest by her grandmother to solve a family mystery.