Thanks for all the advice - Stefano a.k.a. nenonano provided the finishing touch.
I now have inline HTML after making the change to:
/etc/e-smith/templates-custom/home/httpd/html/horde/imp/config/mime_drivers.php
and doing expand-template on:
/home/httpd/html/horde/imp/config/mime_drivers.php
Does this principal follow for all the configs in Horde?
Many users at this site are now extremely chuffed
