The aircraft now in the RAFM was actually made ready for filming, and light meter testing done. The engine had been run, and it was proposed to make it airworthy for filming, a structural and mechanical survey indicating that this was possible, with relatively little work, as the airframe and engine were in good condition generally. However, although the expense of doing so was a hurdle, the main factor preventing its use was the potential risk to such a valuable aircraft, it being the only completely intact example still in existence.
Here's some shots of the Ju87 at the time of production of the movie, one showing it rigged in flying attitude for the light meter tests, and a shot of one of the 'Proctukas', as they were called.
The two B&W pics were published in 'Flight International' in 1969.