The wizard in my shed : the misadventures of Merdyn the Wild

"Merdyn the Wild is from the Dark Ages. He's the world's greatest Warlock (don't call him a wizard), banished to the 21st century for bad behaviour, and he's about to create a whole load of trouble for Rose, aged 12. Rose is a totally ordinary girl, on a mission to mend her broken family. Bubbles is Rose's guinea pig. He just poos a lot. When Rose bumps into Merdyn and discovers what he is, she quickly realises that he could be just what she need...