I'm trying to remember the name of a children's book I read over forty years ago. I don't think it was a new book even then. It was a chapter book, about the level of the Famous Five books.
It involved a sister and brother along with their parents spending a holiday on the Isle of Wight in an aunt's vacant house (Great-Aunt Loo?). The aunt had adopted a girl named Andy (Andina Petronella) who spent the holiday with them and who made up imaginative stories about her background and about everything else going on around them. There were other children in the story too, one called Podge, I think. There was a Mr. Butterworth who came in at the end of the book. I first came across the word 'crustacean' in that book.
Does anyone know what the name of this book is? I have happy memories of it and would love to read it again.