Manderley is a fictional estate in Daphne du Maurier's 1938 novel Rebecca, owned by the character Maxim de Winter. Located in Southern England, Manderley is a typical country estate: it is filled with family heirlooms, is run by a large domestic staff and is open to the public on certain days. It is often said to be in Cornwall, as this is where the author lived, and the nearby placenames "Kerrith" and "Lanyon" are Cornish-derived; the film version is explicitly set in Cornwall.
https://en.wikipedia.org/wiki/Manderley