The movie is actually based on the bestselling and Whitbread Prize winning book Georgiana, Duchess of Devonshire by Amanda Foreman. The book about Georgiana began when Foreman was working on her Ph.D. thesis at Oxford and came upon a "cache of her letters" and then fell in love with her subject. She also served as historical adviser where she also gave the actors insight into the lives they were portraying.
The Devonshire estate of Chatsworth (above and below) was of course used in the movie which is also amusing since it was used as Pemberley in the 2005 version of Pride and Prejudice also starring Kiera Knightley. Other scenes were filmed at Kedleston Hall in Derbyshire.
I know I am looking forward to learning more about Georgiana, Duchess of Devonshire, the It Girl of her day. From the sounds of it, she could give Paris and Britney a run for their money! As the retired French diplomat Louis Dutens, who wrote a memoir of English society in the 1780s and 1790s said, “When she appeared, every eye was turned towards her; when absent, she was the subject of universal conversation.”