All very interesting. Re-reading the relevant chapter in Jon Pressnell’s excellent book on the traction there is the suggestion that another genuine 15/6 convertible exists with 1946 homologation. Also the intriguing possibility that two rolling shells were acquired in 1959 by a Parisian garagiste and built up into complete 6 cylinder roadsters. Now it would be nice if that were true and one of them was in the film, but surely they would have been accounted for by now and documented somewhere???
Peter Fereday