Good news, David. While I was searching through Constance Radcliffe's notes for the Ballajora "Dick" family for Kevin (please see my recent answer to him) - notes which came to me via my Corkill cousin who still lives in Maughold and who was a friend of CR's, I found a Patrick Corkill = Catherine Creetch chart which identified son William Corkill b.1816 as "at Jalloo 1851, m. Jane Stowell (Bride)".

Still not 100% proof, but the families were within living memory of many of the people the Radcliffes would have been talking to when compiling the social history which became their Maughold book, and as I thought I'd found your alternative William unmarried in 1851, it is looking good!

Now we need to link up this William's son John with your one in NZ.

Sue