I've had another thought, Jean. If she was illiterate, she may well have memorised how to write Elizabeth Sayle. On marriage to John Corkan, she may have memorised a six letter name. But what would she make of a ten letter name like Sidebotham? If you were having to practice the shape of the words (as opposed to being able to read them) it might have been too much of a task.

Your revelation about John and Elizabeth Corkan going to Salford explains why she was in Lancs. However John died in Kirkmichael. Did they travel back to Man so that he could be with his family? We'll probably never know, but Elizabeth must either have stayed in Manchester or returned there for her to meet up with my great grandfather. Perhaps little Elizabeth stayed on the Island and perhaps died there.