Hi Rob,
I think you originally thought your family came from Maughold - possibly from the Ballajory "Dick" Corkill family?

Then there was a long thread under "Ancestors of Thomas Edward CORKILL 1876-1944" which included a lot of information from Eric Gelling.
Was TEC your ancestor, and was Eric's information not about the right family? - Just trying to see where you are up to, because I don't remember John Thomas Corkill & Elizabeth Caine from previous messages (which is not to say they are not there)! Could you refresh my memory please as to how you traced back to that couple?

Bapts found on Familysearch are:
John Corkill christening 15 Oct 1819 MAROWN,ISLE OF MAN,ENGLAND
parent Jon Corkill, Eliz Caine

Elizabeth Corkill christening 15 Oct 1819 MAROWN,ISLE OF MAN,ENGLAND
parent Jon Corkill, Eliz Caine
[so same date as John's bapt].

Catharine Margaret Corkill christening 18 May 1821 MAROWN,ISLE OF MAN,ENGLAND
parent Jno Corkill, Eliz Caine

Edward Corkill christening 12 Oct 1823 Marown, Isle of Man
parent John Corkill, Elizabeth Caine

Ellen Corkill christening 12 Oct 1823 MAROWN,ISLE OF MAN,ENGLAND
parent John Corkill, Elizabeth Caine
[same date as Edward]

Thomas Corkill christening 02 Oct 1825 Marown, Isle of Man
parent John Corkill, Elizabeth Caine

William Matthias Corkill christening 17 Feb 1828 Marown, Isle of Man
parent John Corkill, Elizabeth Cain

Their father was transcribed as John or Jon - not John Thomas, although he married as John Thomas Corkill 2 Nov 1816 Marown.

There was a later John Thomas Corkill & Elizabeth Caine having children baptised in the 1830s in Baldwin St Lukes.

Sue