Thank you Nathan. Worked a treat.
For a file such as the assembly file, is it better practice to assign the render material in the assembly file and to leave the files used as blocks empty? I am deliberately adding the blocks as “active” as opposed to “referenced” in order to consolidate the building material in the assembly file and to be able to render by layer and not by object.
I was thinking this may have the added advantage of being able to save the block files as “save small”. Is this the case?