London, Kent and Eastern England (particularly Suffolk) seem to be the most prone to this, primarily because of what was dropped on it by the Germans, Americans and British. In our area in particularly you're more likely to find British munitions than German since the whole area south of the river here was used as a live fire area, they even moored a warship off the coast so it could shell the area to act as enemy artillery...only one day it aimed in the wrong direction and shelled the town...
They built a mock-up of the Atlantic wall to figure out ways to breach it and test Hobarts funnies.