The "Bristol Post" had a link to a site where such posters could be purchased. That U. K. site offered the posters at cost of about 10 pounds (approx. $15) - which leads me to believe that they are reproductions (not originals).
Nevertheless the posters are charming. I would guess that they date to the 1950's.
Here are my favourites:
|Clifton Suspension Bridge GWR and LMS|
|Bristol Cathedral, where I was made Deacon in 1976 GWR|