These are the books by Helen Cresswell that are reviewed on this site:
A funny little bit of magic leads Griselda Dogberry into another world. But baddies are after her.
Minty finds that the sundial in the grounds of the old house holds the key to time travel, but can she do any good deeds while she's hovering about in time and space?
A none-too-successful guardian angel does his best to protect Ellie from The Boss.
Lizzie Dripping always has her head in the clouds. Short stories.
Surrounded by a brilliant family Ordinary Jack would like to feel a little less ordinary, just for once. A scheme is laid for a brilliant practical joke...