A bit of information about the film IF.
When McDowell and his mate steal the BSA [?] motorcycle from the showroom they are seen to ride off. The next shot is them riding north along the A5 road just north of Redbourne, Herts. They slow down and pull into the J&H Cafe, a shot of the sign is clear in the film. I knew this location well, because from 1967 to early 1968 I worked for J&H Transport at the garage next door. The Cafe was owned by the Transport Company. The site was to the west of the A5 Road, about 100 mtrs south of what is still the Packhorse Public House on the road that goes to Whipsnade Zoo. Not a good place to eat, but seemed OK for a naked romp.
The site has now been cleared of the old cafe and bungalow used as the area office. A chain-operated petrol station now occupies the site.
If I remember right, J&H was June and Headley Transport.
Yours, John Morgan