Have you tried opening multiple files and cutting and pasting from one to the other. Select the contents of one file, then select EDIT, COPY just like you would do in a word processor. Navigate to the receiving drawing, then select EDIT PASTE. The parts will drop into the receiving file, but will need to be moved around to where you want them. Repeat for the other files until you have the entire assembly.
BTW, I seem to remember at least one book on the Quorn and have seen it in magazine articles over the years. It is a well known and well-respected tool system. Missing bits should be able to be found. Let me know if I can be of help in this area.
Rendering the complete assembly should be do-able if you would like to go that way.
Hoping this helps,