There's a Best Children's Book prize in the British Book Awards too. These awards - known as 'The Nibbies' - are given out for excellent writing, but also for how popular a book is.
Eoin Colfer won the kid's prize in 2001 for Artemis Fowl. And Philip Pullman won the best overall author award for The Amber Spyglass. Again, it's really unusual for a children's author to win this prize.
Most of the other prizes in these awards are for adult books though.