Hello Morag. I am not sure whether you are still looking at this but I have some information which probably will not help re John Costain but you may find of interest. In a response to your initial post, Margaret Costain is shown as one of the sisters of John,(b 16/5/1858), married to ?Quilliam. I have a copy of the Baptism register entry showing Margaret as Baptised on the above date and daughter of Thomas & Margaret (Nee Moore) Costain. Margaret Costain then married Samuel Quilliam in Castletown on 3/11/1862. My mother was married to their youngest son Ernest from July 1934 to Dec 1940 when he was killed in a bombing raid on Liverpool. My mother married again and I am her only son.