My sisters and I watched this series in the late sixties, when we were all pre-teens. And of course, we also saw both of the movies.
Yesterday I watched a VHS recording of the movie and loved it! Since it was over forty years since the first time and I remember only names/faces from the show, it was like watching it with fresh eyes. Yes, I agree that one does not have to know the show or even to have seen it in order to enjoy the movie.
As an adult, I now appreciate the mood and excellent use of sound and lighting in the movie. The scene where Carolyn calls out to his fiance and he goes to her was visually stunning. The funeral scene and the costume dance were also memorable.
At the time this was an unheard-of amount of blood for a movie, much more than the Hammer horror films of the time. My mom had to think long and hard before allowing 11 year old me and my 10 tear old sister to see it. Nowadays the blood looks like poster paint, but the good acting and great production design make up for it.