Just a comment on the Vans, I worked as a mechanic in the 1960's in a BMC garage. We used to detail the new cars when they were shipped down to country NSW from Sydney as they had protective wax on them which was removed with white spirit, anyway I remember a particular, brand new Mini Van arriving with a fold down rear seat that when folded down the floor was still the same as a normal van except for the cut to allow it to fold up. I believe people wanting this could arrange for it through the dealer who then had the factory outsource the conversion before shipping. I believe it was a Leyland Mini van.
Cheers, Frank