I think after a bit of research it my initial guess was thistle family, but now I think it is probably a dead Sea Holly flower which is a member of the thistle family. Especially as it was found within the sand dunes.
Not an expert on British plants, and not an expert of varieties of holly, but the leaves, including the green ones in the background, immediately reminded me of holly. Whatever it is, you photographed it well. Someone more knowledgeable certainly ought to be able to identify it from your shot.