Is Fleur a type of flower? I just thought it was the French word for flower. Not knowing it's a type of flower meant I wrote off the the idea of a 'flowers' group, and stopped me solving any of the line

Good ideas - really fiendish, but I'm not sure there's only one way to sort the items into the given groups. For example (SPOILER WARNING) Minerva could move from the Potter group to the Roman goddesses group, Victoria could move from the Roman Goddess group to the Doctor Who group, and Susan could then move from the Doctor Who Group to the Harry Potter group.