Hi Tricy,
I have a copy of the movie "Adventure in the Hopsfields", so I can confirm that it's not about a treasure hunt. It's about a little girl who runs away from London to join her friends who spend the summer in the country harvesting hops. Nearby are two windmills.
However, I just found 76 windmill movies in the imdb with plots, maybe your film is included:
[
www.imdb.com]
To my great delight I also found the collaboration function again which was missing in the imdb for at least the past one or two years :(. It used to be below every actor's filmography and then it was gone at some point. So I'm very happy that I found it in "extended search" where I also found more windmill movies for you.
The collaboration function was useful to figure out for instance how many movies Myrna Loy and William Powell made together.
I hate those useless web designers who always have to either remove functions that were useful or hide them so well that users cannot find them again. If they simply could leave the imdb the way it is and NOT mess around with it!
I've recently watched "Le trésor des treize maisons" [
www.imdb.com] and it's not about a watermill.
I agree, these wonderful old CFF movies from the 50's and 60's are treasures!!!
Cheers,
C.