Ali Sparkes is a great author who has written many, many children's books. Her first series was the Shapeshifter series. Currently she seems to be writing stand alone sci-fi and fantasy books. I have enjoyed reading all of them.
In this book Eddie is having to spend the summer holidays with his not particularly nice Auntie, and his even worse cousins. Bullied by Damon, his ear drums bashed by the dancing/singing girls it looks like being an awful few weeks. But on a trip out to the caves nearby he meets a girl who shows him many, many adventures and changes his life forever.
The author, Ali Sparkes, strongly suggests that you visit this website to get a feel of the setting for the book. www.wookey.co.uk/caves.htm