Thanks chaps!
The car I first saw with these fitted is currently for sale at Woodcote, having been bought by them from a private seller in North Yorkshire. It was him who told me about them. However, it may be that the owner prior to him made them from some form of pliable carbon look overlay. Whatever way it was achieved, it was a very effective way of covering up all the small cracks that appear towards the front of the wing without the cost of new wings.