OK. I'm calling a halt to this now but I will make a few points.
The seller of the film owns the film and can do what he likes with it providing he does not make a copy of it, or broadcast it or in fact screen it at a public event without acquiring theatrical rights from the BBC's commercial agency. The copyright in the film is owned by the BBC and the third parties contained in the motion picture and soundtrack.
Making any copy of the film (apart from reasonable still images to show the state of the film for the purposes of its sale) could be construed as a breach of the BBC's rights at which point the ownership of the physical film could legally be disputed by the BBC.
I have been in constant contact with the seller and despite numerous requests he has decided not to loan the film to the BBC, although he says he recognises its cultural significance. More than that I can't say about what we've discussed, but it's not helpful shouting about the rights and wrongs of it here.
Please don't start another thread about it. The film will sell for some ridiculous price way beyond its physical value (I pity whoever has to stump up the cash) and a copy may end up at the BBC. Time will tell.