Trish,
I had a look into the meaning of "No Cure of Souls" (next to your post for William Thornhill in 1851) and found the following:
"The man concerned was a cleric or clergyman of the Church of England. He
held the educational qualification of "Master of Arts" (A.M.; or today
often termed M.A.) and was therefore most likely a graduate of Oxford or
Cambridge University. "No Cure of souls" means that he was not at that time
appointed to a position in any parish; either as a Curate, Vicar etc. To
hold a "Cure of souls" is to have the care of souls - to be in spiritual
charge of parishioners."
http://archiver.rootsweb.ancestry.com/th/read/DEVON/1999-11/0942310772The article then refers to some published alumni lists for Cambridge and sure enough it is online and I found William.
http://www.archive.org/stream/p2alumnicantabri06univuoft#page/174/mode/2upHas a lot of good info, including birth/death date, who he married etc.
Paul