Question Author
Not 100% sure (been looking at island books on web) but hopefully will jog someones memory-although it was planet, not island- the word Eigg was in the book-she was banquished there-so maybe she was a witch-I don't know why I remember start so wee, but not title or auther-been looking (AGES) at 'books like this' under Mary Poppins on 2 sites, but nothing like it-I think pb cover was her and kids. I remember at the time of reading it to son(90's) I hadn't heard of author, so possibly a first book that wasn't popular?