Double bill with Slave Girls-release dates-confusion and clarity

Hi, this was released in the UK as a double bill with Slave Girls (1966)(aka Prehistoric Women), another Hammer film. There is even a double bill cinema quad poster that exists from the time which is now quite rare. Does anyone know of the actual UK release date for the double bill and was it a reissue release. All I know is what imdb states here which is pretty much repeated on the internet elsewhere: UK release date Slave Girls 7 July 1967, Devil Rides Out UK release date 20 July 1968. I have read Slave Girls was first released as a double bill with The Devil Rides Out and was cut from 91 to 74 minutes and as per the trivia section of Slave Girls is because it was a considered a much weaker film. But this does not tie in with the UK release dates published for each film which are a year and 2 weeks apart. The BBFC website is also missing details of the cut version of Slave Girls so it also cannot help. Any diehard Hammer horror fans know the actual details of when the double bill of these 2 movies occurred?