I've never heard of this children's story, but this short film has been making the rounds on several animation blogs. I did see the documentary before first ever seeing the film. Apparently they made actual model sets then later added in the CG animation. It gives the film a similar texture the illustrator captured in the book. I recognize some of the celebrity voices, like Robbie Coltrane, Helena Bonham Carter, John Hurt and Tom Wilkinson.
"The Nation s Favourite bedtime story is being brought to life in an all star beautiful adaptation of the best-selling book by Julia Donaldson and Axel Scheffler. The Guffalo debuts on BBC One this Christmas and comes to DVD in time for Easter 2010. The film's all-star voice cast features Robbie Coltrane as the Gruffalo; Helena Bonham Carter as the narrator; Rob Brydon as the Snake; James Corden as the Mouse; John Hurt as the Owl and Tom Wilkinson as the Fox. The Gruffalo tells the magical tale of a mouse who takes a walk through the woods in search of a nut. Encountering three predators who all wish to eat him a fox, an owl and a snake the plucky mouse has to use his wits to survive, creating an imaginary monster who then turns out to be only too real."