(Photo's from The Western Telegraph) The house seen above was apparantly used for some interior shots for the film and the other pic is of Cillian Murphy on set. We roamed around Tenby on our search but couldn't find the filming or any proof re: The Colin Firth rumour. There were people who'd seen Sienna Miller and Keira Knightly though.
The males in our party were not very fussed about looking for either of those two ladies and when we couldn't find Colin the females kind of lost interest too, and we abandoned the quest. So, is Colin Firth in the film? I really don't know but it was fun looking for him.