Trix UK-outline models do not feature often on RMWeb. Although they featured some interesting prototypes, their 3.8mm/foot scale made them unsuitable for use with other 4mm/OO stock.
However, the plastic pig iron and mineral wagon bodies were fortunate as this meant they scaled at a correct prototype 16'6 ''.
There is no kit or rtr version of a pig iron wagon in 4mm; Peco produce a 7mm version, and Farish a 2mm. I believe Mainline announced one in 1982??, but it was never produced as