Around 25 or 30 years ago, D&S Models in England brought out a brass and white metal kit for the Cowans and Sheldon 15T crane. Actually 2 different kits, with different shaped jibs. They were widely used in England on the NER, GWR and many other railways in between all with locally sourced runner wagons.
While digitising drawings in the IRRS Archives 5 or 6 years ago, I came across a nice drawing for a 'GNRI 15T Breakdown Crane'. It was pure Cowans and Sheldon. Identical other than the gauge. When I showed the drawing to the proprietor of D&S, he was very impressed because when he was doing the kit he consulted Peter Tatlow who wrote the definitive 2 volume book on Cowans and Sheldon cranes, but Peter did not have very good drawings, and some of the 'works' in the kit was a bit sketchy. (Guess how it goes yourself - style)
Looking at photographs of such cranes, the shape of the pipe-work around the boiler seems to differ on each crane - maybe it was replaced over the years.
I don't share Leslie's optimism in seeing a ready to run model as soon as 3 years hence, and I doubt that it will be anywhere near the initial advertised price.