If you are trying to find your Manx Kerruish ancestry, can you find the marriage and death certificates of your immigrant Kerruish ancestor, which could give his age and names of his parents? We could then have a go at finding his baptism on the Island.
Try me at that stage, but in any case try contacting Liz Newland, ozimanx@rie.net.au. She knows a lot about Kerruishes.