Hi Janette,
I'm glad it is all fitting together so well for you. The William in the censuses certainly looks like your one, so I hope the NZ certs don't throw up anything unexpected - I look forward to seeing what they have.
It is also helpful that David has researched this family, and he may be able to throw some light on what happened to their parents if his James Joseph turns out to be the same James. It is frustrating not to be able to find their baptisms, but IOM marriage certs have fathers' names and occupations as well as addresses etc., and the witnesses' names at James Joseph's marriage might also be useful.
Sue