If you want to know anything about D Wickham & Co. Ltd, I suggest you join the Wickham of Ware Facebook, Flickr & Yahoo! Groups.
There is also a book (published by Rockingham Press) about the Company but unfortunately it is out of print now.
With regards to the Lightweight Dumpers, I would be very interested in any information. In the last 8 years I have seen two sold. One at a Cheffins Auction in Cambridgeshire & one on eBay.
If you know of any surviving examples, details would be very much appreciated.
Thanks
Jonathan
Owner & Moderator - Wickham of Ware Online Groups