Hello Stephen I found your query on the web and the information I have is that Wm curnow b 1782married Sarah Roach b1794 at Towdenack in 1815. They had 16 children of which the other Wm Curnow you mention was born in 1818. the names were john b 1815,thomas b 1817, william b1818, sarah roach b1820, christian b1822,isaac b1823 d1823,jacob b1823 d1823,(twins) isaac b1824 d1825,jacob b1825 d1892, elizabeth mary b1826,jane b1827, jane(2) bca1828, mary ann b1829, eliza whipdale b1830, isaac roach b1833, honour b1835.. The isaacs and jacobs were twins born back to back. William curnow b1849 son of Wm Curnow b1818 was the person who went to cumberland and worked in the mines. He actually jumped ship in Whitehaven.
I have other information going back to Thomas Curnow married in 1778, if it is of any use to you I will be more than happy to let you have it. just email me on email@example.com anytime.By the way my mother was one of this Curnow family.