I too have him in my family tree though I believe his real name was John Boseley (Bozeley)Mayne. He did die, or at least was buried, on 29 Sept 1780 in All Saints Church North Moreton according to the Parish Transcripts. He was baptized on the 3rd April 1736 s John Mayne son of Philip b 1700 & Mary Bosely b 1706 in N Moreton daughter of John and Sarah.
He and Mary Leaver married on 25 December 1757 in North Moreton and the witnesses were Abraham Gregory & Frances Field.
I am currently copmaring notes with another family member who has the Mayne family tree. If you have more details I would love to see them.
The above information is gleaned from the Parish transcrips of North and South Moreton