I will keep my eyes open.
I looked up John Corkill, who served in the Royal Navy in "A Manx Notebook".
He went to France, not Cornwall:
"John Corkill, of Squeen, who served in the Royal Navy during the French wars, and who afterwards married a French countess and resided in France for the remainder of his life, was also a native of this parish. He left a fortune of three millions, which is still held in chancery for his heirs, they being the children of his only sister, who married John Kneen of this parish."