For the scene when Miss Potter and Norman Warne say goodbye at the train station, the script says "exterior rain". Though Ewan McGregor suggested covering the clothes in glycerin to simulate the soaking wet look and to avoid having to actually be drenched, costume designer Anthony Powell insisted the actors be heavily sprayed down for the scene to look authentic. Ewan McGregor was made a very thin wet suit to wear under his costume so he could stay warm.
In the railway station scene filmed on the Bluebell Railway, the LNWR on the tank locomotive has been very visibly altered from LWSR. The N stuck over the W is a really bodged job for such a close up shot.
In the film the book "The Tale of Jemima Puddle-Duck" is shown to be published followed by "The Tale of Two Bad Mice" then "The Tale of Mrs Tiggy-Winkle". In reality "Two Bad Mice" and "Tiggy-Winkle" were released in 1904 and 1905 respectively and "Jemima Puddle Duck" wasn't published until 1908 with five other books in the intermediate years.
Beatrix Potter: We did it! Did you hear my heart? It was a kettle drum! You see, we can't stay home all our lives! We must present ourselves to the world, and we must look upon it as an adventure!
Beatrix Potter: [voiceover]
There's something delicious about writing those first few words of a story. You can never quite tell where they will take you. Mine took me here, where I belong.