There is no such place as "Haynes Cemetery". In fact, there was no such thing as a cemetery in 1718 - the word only came into general use in the 19th century when the overcrowding of churchyards forced the establishment of private and municipal grounds for burial outside urban areas. Your chap would have been buried in a churchyard (or within the church itself if he was rich). You will need to search the burial registers of a great many parishes if you cannot be more precise than "London". What is the documentary evidence for his date of death?