other than Plus Model, is there a 1:35 trailer being manufactured? thanks

Mirror Models' 10 cwt Trailer #35150. The kit contains 2 ! WWII era trailers "suitable for average modelers" (printed on the box)
Haven't built one yet but does look nice.

You use the expression "Caravan" so I assume you mean a model travel trailer as with something a person could sleep in??

There are a number of model trailers out there but not many (or any) "travel" trailers.

correct; perhaps something to ease the housing shortage immediately after "The War".

I have resigned myself to a scratchbuild, and subsequently order this book: https://www.amazon.com/gp/product/1906133468/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

and saved more YouTube videos than is healthy!

thanks. if I go small, this actually looks like a good jumping off point.

http://www.mirror-models.com/35150/10cwt_assembly.pdf

In real life there were several WWII era civilian "Caravans" converted to mobile photographic labs during the war. I will see if I can find some photos.