Earlier this afternoon while mulling things over I worked out the name of the third writer from the clues I could remember and thought I was very clever. Well, when I got home later and looked at this again, I got the biggest self-kicking 'duh!' moment I have ever experienced in all my cruciverbal years!
I now understand it all, especially the meaning of the 'advice to solvers'.
Although I worked out the names of all three writers myself, I spent a lot of time confirming them on the internet and this turned out to be unnecessary. I have been well and truly suckered.
I will say no more for the present but will monitor this thread in case anyone needs a little advice.
(What a plonker I am, really!)