The solution I found involves adding a 3rd party module (contrib in SME jargon) to SME Server which is the SMEServer Loginscript. This adds a tab to the SME Server Manager Console from where you can use a combination of user and group orientated IF statements to control which drives are mapped depending on who logs on. More functionality is also available.
To install this, I logged into SME Server as Root (to access the terminal prompt), then used wget to download from:
http://mirror.contribs.org/smeserver/contribs/jbennett/sme7/loginscript/RPM/smeserver-loginscript-0.2-8.noarch.rpmA local install on SME Server was also done from the root terminal prompt:
yum localinstall smeserver-loginscript*.rpm
Solution was taken from SME Server forum pages:
http://forums.contribs.org/index.php?topic=40642.0