Jo, thanks for your help. It would be 1931 that John Kelly would be 8 but Frances says there was no census available then.
In Lawson's 1841 census I see 2 Johns in Castletown - one aged 19 ref 1464/5 23 8 and the other aged 18 ref 1464/5 49 17. In the ref 49 17 there is also a 45 year John K. The younger John eventually became a painter & dec. I really need to know where both these John Kellys aged 18 & 19 in 1841 were living, with whom they were living & their jobs. Having this info could get me one step nearer finding the parents' names.
As you have found out there are so many John Kellys . I wrote down all the Kellys in C'town from Lawson's list to see if any names could be matched but my brain is working overtime & not producing much ! Any further help with the original 1841 census would be greatly appreciated.