When I registered my Ford GPW I had no paperwork with it so I joined the MVT but they wanted to inspect it. where as Rex Cadman gave me a letter based on the chassis no together with some pictures showing the important bits (the cut out on the dash, blocks on the bonnet and rear box covers) and the chassis no as stamped on the frame.
My DVLA guy was a real pain to he made me sit out side in late November for over an hour then we had a pointless discussion about the colour after all green is green. Still he gave me the reg no so no problem.