A chap posted an old clipping from the Shoreham Times of 1957 showing the filming. The quarry used for the crash was a much older and smaller one than the cement works. I'm sure it's all earlier in this Thread..... or another one very similar. Another poster recalled seeing the lorries next to the trees. It was near a radar station he worked at. I'm sure you'll find all this upthread.
Great that you've got your finger out and been there though. I keep driving past on the A27 and keep thinking I must pop up there some day..... I'll look forard to seeing some pix....