Thanks for the ideas.
I'm soooo tempted to use this one by Noel Coward:
We're just waiting for the moment his poetic licence expires.
I've started drafting the third book which is also about writing poetry. For that, I've found:
Today, the main difference between poetry and prose is that, dreadful though it is, poetry doesn't go on for nearly so long.
That's by Richard Ingram and if I decide to use it, I know I'll have to get his permission.
I've already got permission from Adrian Mitchell to use:
Most people ignore most poetry because most poetry ignores most people