Thanks GR2, that's great work! Thanks so much.
I too hadn't had much success in finding James Horn's marriage, or Jean's mother's name on her birth or marriage documentation. I hadn't given up yet, but following William through was a good thought.
I got a copy of Williams death documentation as you suggested, and it did indeed show that Ann Tough was his mother. But it names his father as "George Horne Crofter (deceased)".
I've done a quick search and haven't so have been able to find a plausible George married to Ann and father to Jean or William. So is this another couple or could they simply have recorded the wrong name? (Perhaps his second name was George, or he was known as George for some reason? Or he died young and William never knew him so didn't know his name??)
I don't have enough experience to judge that. What do you think?