Hi Alan,
Sometimes the Ancestral file is OK, especially when they give sources, and the LDS staff at FHCs often think they are helping people trace back quickly by using someone else's research. But you are right that this can't be trusted - you need to check back one generation at a time, and order all those films of parish registers and wills, etc., available through the FHC. For example, you need to check the spelling of Cath's surname in the parish register at the time of her marriage 15 Aug.1809 Braddan: LDS film no.0106709.
- And look at their children's bapts on film to see whether any clues are given, such as a place name.

Brian Lawson's indexes could help. e.g.
www.iomfhs.im/lawsons/burials/cottier_a.html
www.iomfhs.im/lawsons/wills/co5-will.html
www.iomfhs.im/lawsons/census/census_index.html

Sue