Thanks to you both
@Turtle91 Looks like I need to clean out the CSS. The one I use now is
.fn { font-size: 67%; vertical-align: text-top; } /* With thanks to Weatherwax */
The one I quoted earlier is old stuff.
I have indeed put the filename in front of the #F1, just as I've changed the number as more endnotes were added. As I've mentioned in earlier posts the test file I used works perfectly well on my Sony. The questions I'm asking are about designing for the Kobo, not about html or ePub.
About the span: here is a fragment from the html
<p> ..... country quiet, of his mother,<span class="fn" id="F2"><a href="Endmatter.html#N2">[2]</a></span> of poetry – ....</p>
I'm not sure how I could set both the features of the a and its id without a span. What do you do?