I have downloaded the Debian package big-cursor (I have sadly given up on 
comixcursors for now - I'll try again in Stretch).  It is definitely there:

brian@Linux:/usr/share/fonts/X11/misc$ locate big-cursor
/usr/share/doc/big-cursor
/usr/share/doc/big-cursor/README.Debian
/usr/share/doc/big-cursor/changelog.gz
/usr/share/doc/big-cursor/copyright
/usr/share/fonts/X11/misc/big-cursor.pcf.gz
/var/cache/apt/archives/big-cursor_3.9_all.deb
/var/lib/dpkg/info/big-cursor.list
/var/lib/dpkg/info/big-cursor.md5sums
/var/lib/dpkg/info/big-cursor.postinst
/var/lib/dpkg/info/big-cursor.postrm
/var/lib/dpkg/info/big-cursor.preinst
brian@Linux:/usr/share/fonts/X11/misc$

But I cannot find a way of persuading Trinity Control Centre mouse themes to 
see it.

Any suggestions?  Or any other suggestions as to how I can get a large, 
preferably red, cursor (but any large one will do) in Debian 8 and Trinity 
14?

Thanks.
Lisi