Ref Penzance John being son of John Corkill & Margt Cashen -
The only thing I have found that might question this (if I have got it right) is that on the extended family tree info on IGI, it looks like he (bapt 1770) ended his days on the IOM?
I have been trying to work backwards from 1893 and Eleanor Ann but start to stumble after the 1871 census.
Could her father John be John Corkill born 24 March 1811 son of Thomas and Elinor Callow?