Chesham Park was used for the scene when Natalie meets the jogger, played by a then unknown Pierce Brosnan and credited as 'Last Victim'
The house that 'Last Victim' and Natalie go to is just across the road from the park, on Chartridge Lane.
The Silent Scream
The infamous pet shop is located in Broad Street (Just down from the High Street).
The hospital scenes were filmed in Chesham Cottage Hospital (now derelict). Thanks to Moyb Ullah for letting me know about this location. He found it in a shooting script for the episode that he aquired on from 'mem posters'.