My dad David Garland found this Post Office 404 page today. It's informative and the guidance links at the bottom help the user decide where they should go instead.
Although I do wonder if they might benefit from using this image from Longleat Postman Pat Village too.
(That has actually reminded me of a childhood memory, when my gran knitted me a Postman Pat doll as a present. She took ages on it, it was perfect. She presented it to me and instead of being delighted, I cried. It's head was so long and floppy that somehow it made me really sad for Postman Pat.)