The majority, that are clear enough to identify, are very similar, if not identical to the Morris CS4 aero-screens. I wouldn't be surprised if there were other makes, but in most photo's the quality is too poor to get a positive ID on the origins of the aero-screens. The Bedford Aero-screens look like they could also be an alternative with possible examples attached. Looking at the details they would be easy to fix to the wooden dash surround.
Photo credit to Jack Neville -
http://www.mapleleafup.net/forums/sh...-screen&page=2