Who is Hello, Goodbye and Manythanks from The Girl Who Circumnavigated Fairyland in a Ship of Her Own Making and what is their importance?

These three characters are the first people September encounters when she arrives in fairyland. Hello and Goodbye are female witches, while Manythanks is a wairwolf, a wolf that, at a certain time of the month, turns into a human (this is the opposite of werewolf). They have the power to see the future in the soups and/or potions they create but, when September asks about HER future, they are reluctant to tell her. Goodbye explains that her magic Spoon was stolen by the Marquess, and that she needs someone like September to retrieve it. In other words, she sends September on to the next phase of her quest.