Athough, when I found the impaled Brick, I wondered whether a Shrike had been responsible, I dismissed the idea, because to my eyes, the site didn't seem suitable; leaving accidental death the other option. Following comments made by George, Dave and Howard about the ppssibility of it being the victim of a Shrike, I examined the specimen (Luckily, I collected it) and apart from the gaping hole made by the gorse spine, which is near the rear end of the abdomen, there is a large area of abdomen which has been crushed, close to the thorax.
Although it doesn't show up particularly well in the photo taken through my microscope, the crushed area is of a shape that could have been made by a bird's bill and on the thorax there is a discrete area where the hairs have been removed.
Based on the appearance of this damage, I think it entirely possible that a bird; probably a Shrike, was responsible for the impalement of the moth.
I wonder if it is still there???