Thanks for the reply, Hitch.
Doing the pop-ups is no problem. All you need for that is a link and a back-link and, as you rightly say, it just works, but sans italics.
The italics themselves are fine. If I use the "Go to footnotes" link at the bottom of the pop-up to jump to the full-page version of the footnote, then there the italics are in all their splendour. They just don't show up in the pop-up; they simply show as plain text.
If you're seeing the same thing, though, then I won't worry about it; I guess that's just the way it is
.
Many thanks for the help.