Have you tried any of Dick King Smith's books? My 7 year old son loves them. He liked the short stories in Back to Front Benjy and I'm just about to try the Water Horse. He also likes the Narnia books.
Read "The Hodgeheg" and enjoyed that, didn't know there were others. We have also read the Cressida Cowell "How to ... a dragon" which went down well and also just started the Astrosaurus series. Thanks for the information.