Many thanks Diapason. The clue was in the walling surrounding the doorway in your pic, which appeared to be of of chalk blocks. It is supposed because of this building material, and the shock of big military guns nearby during WWII that the church suffered seriously with plaster falling from the walls and ceilings, doors being blown open through shock and windows being blown in. Whether the military contribution caused the collapse of the nave roof and nave during the 1950s is debatable, as the church's structure had been poorly maintained for many years. It is also suggested that heavy rain and a flooding lake close by caused the chalk blocks to absorb water and fracture.
I will post my next later tonight