Thanks to jester and the author of smeserver-dar2 this problem has been solved. For me anyway...
I'll summarise things so that others can take advantage of the work/research by jester. It worked for me but there is always the possibility that it won't work for you.
1) Create a file called usb-rev35-drive.fdi in the /usr/share/hal/fdi/95userpolicy directory, populate it with the code below.
<?xml version="1.0" encoding="ISO-8859-1"?> <!-- -*- SGML -*- -->
<deviceinfo version="0.2">
<device>
<match key="storage.bus" string="usb">
<match key="storage.vendor" string="Iomega">
<match key="storage.model" string="RRD">
<merge key="storage.policy.desired_mount_point"
type="string">usbdisk</merge>
</match>
</match>
</match>
</device>
</deviceinfo>
NOTE: If you have other USB disks attached you might have to change the part where is says usbdisk to something like usbdisk2 or usbdisk3. Check fstab for this.
2) Install smeserver-dar2, follow the instructions of wjhobbs found at
http://forums.contribs.org/index.php?topic=34041.0. Just update file versions/names or it won't work. Check
http://mirror.contribs.org/smeserver/contribs//dmay/smeserver/7.x/ for those.
3) Create your backup under smeserver-dar2, the backup target should be /media/usbdisk or what you have changed it to (/media/usbdisk3), no need to add a username or password.
4) Insert a cartridge/tape and run a test. All should be well. There is no need to manually mount or umount the drive because smeserver-dar2 does that for you.
All the above is thanks to those mentioned, I just followed instructions and took it upon myself to summarise it for others.
SME 7.13