Thanks for your comments and suggestions, SBT; I really appreciate them.
- page-break-inside:avoid: Yes, I have, but since this was my first poetry book I didn't want to push my luck. And I'm a bit concerned about having big areas of white space if it's a long verse which only just will not fit on the page.
- return to contents: I'm not sure if that should be there at all. I do not know how people read poetry books; I guess on first read probably straight through, but on later reads probably choose a favourite poem from the ToC, and then want to go to another favourite poem. I've put the links in the toc.ncx pop-up ToC, but some people might think that redundant, and others might actually prefer the quick link back to the contents. Amazon in their ineffable wisdom don't allow access to the toc.ncx ToC.
I'm still feeling my my way on both matters you raise, and may well revise both Sassoon poetry books as time goes on.