Thanks for the reply Brian. It was a long shot anyway. I am slowly tracking down William Conwell. I have now found that he was married to Margaret Lowie in 1839 and had a son. He was listed on film as being "a widower from Marown" at his second marriage. I have also found him in the 1871 Census at Onchan. His son was married in 1878 on the isle, and in 1881 they are all living in England. It is slowly coming to light.
Cheers, Billee.