Just a note about a bit of the info, from checking at the Cornwall OPC site.
http://www.cornwall-opc-database.org/search-database/Catherine Ley was actually baptised in St Cleer in 1777, daughter of Richard and Mary.
She then married Robert Hooper in St Cleer in 1798. (My ancestor the parish clerk of St Cleer was deceased by then or he would have been a witness.)
If you're looking at the 1774 marriage of Richard Ley and Mary Jane in St Cleer, Jane was Mary's surname.

She was a sojourner in the parish while Richard was of this parish.
And actually ... if Edwin Ley 1803 was the landed proprietor in St Anthony in 1851, he was born in Abingdon, Berkshire (and married Cecilia Grantham in Lincolnshire in 1848?). Perhaps his parents were recent transplants from Cornwall and returned. In 1841 his mother was Elizabeth Ley born c1771 Cornwall. Ah, I would expect she was (Mrs.) Elizth Halse who married Hugh Ley, gent, both otp, in Truro in 1788? witnesses Mary and Joanna Halse. Daughter Emma was in the household in 1841 and married Henry Grantham in 1842, father named as Hugh, per record at FS. Daughter Mary aged 20 married in 1803 in Shropshire. This suggests he was previously married, but Edwin born c1803 would be from the second marriage.
He could have been Hugh Ley baptised 1723 Redruth, son of Hugh and Mary. That would have made him a little advanced in age by 1803. Perhaps it was the intervening generation that left the county for a period. Hugh Ley, rector of Redruth, died 1734. This fits with the clergy in the family.
You probably also know that in 1851 there was a John Morgan Ley in Madron who was born in Abingdon in 1795.