Thanks for the input everybody - I think it is Panshanger - as Eckhard posted,I can see clearly on google where the building used to be and the outline of the semi hex of the 'tower' part of the building.I am guessing that the building was demolished to give more parking area (it was looking very delapidated in the movie anyway).Also in all the pics I have seen of the Bellman ? Hangar - it has a large old white oblong 'patch' on the Gable end of the Hangar,this can still be clearly seen on the Google street view posted by DIBO above.
I am always open to suggestions and we will watch the movie again sometime to see if there are other clues.
Thanks again and regards LR