Bill Bedford was notorious for not providing any instructions for most of his etches during the time when he used to run an extensive catalogue. His principle was "IOI" (It's Obvious, Innit)....which was fine if you were dealing with a pair of coach sides, but anything more complex required you to be fully familiar with the prototype or you needed to be able to think like Bill in order to understand how the smaller bits fitted in....or you needed to be the original customer who had commissioned Bill to design the etch in the first place!
I have an etch for a pair of BR Class 25 bogies, which Bill used to produce. The main structure is understandable. The cosmetic parts are far from obvious!