Nick butterworth - Uk childrens author

[Littletiger]

Hi I'm looking for an address for Nick Butterworth, author of the percy the park keeper books. I'm having my son christened in a few months and buying him this collection if books and would love to get an autograph from the author to go along with it. Hopefully it's something he will then treasure in years to come. I've tried contacting Harper Collins by email and they never responded. Thanks