Hi David,
Thanks, every bit of information may help. And yes, all family histories are complex, but some are more frustrating than others!

Clive answers sometimes on this BB, and I think he got some of his Maughold records from Tom Corteen (as I did). Tom lived there and used the original records, so was very reliable. If he wrote that William's bapt on 12 May 1816 included the place name "Jalloo" (which is where William and John were in 1851) then Thomas Corkill and Elinor Callow were likely to have been William's parents.

However, if someone added the "Jalloo" to his bapt record because William was there in 1851, it is very misleading. I don't have it in my Maughold bapt records (but it could have been missed). - We'll have to find someone to check the two 1816 bapts to see whether there was any added information.

Sue