When I first started looking up IGI references on films I made the mistake of only looking at those specific names and dates I'd got from the online index. I later went back and looked at a good twenty years either side of the date and discovered hitherto unsuspected siblings and cousins. I eventually went through the whole film for the parish and noted everyone with the right surname to sort out later, which I wish I'd done in the first place as it was so useful and interesting and gave me loads of valuable information.