We've noticed this strange milky light a lot more since we moved to West Norfolk five years ago, it must affect the whole of the country but because of the big skies it seems more apparent here.
There always seems to be three layers of cloud when this particular condition occurs, the clouds being, no doubt, the filter that produces the strange light. It is almost as if the bulk of the light is retained higher in the atmosphere giving the gloomy appearance at ground level. No doubt there is a scientific name for the phenomena, we must check that out.
All you can do is sit or stand back and marvel the effect, as always it will be completely different in ten minutes.