sagr alug1@suffolk-ancestor-genealogy-research.co.uk wrote: [...]
common "Customer Area" webpage where our customers can type in their login name and password and then be automatically taken to a protected personal webpage listing the files waiting for them to download. [...]
+1 to the comment about using a framework, but if you want to do this directly, the CGI variable REMOTE_USER (so $ENV{'REMOTE_USER'} in Perl and $_SERVER['REMOTE_USER'] in PHP IIRC) contains the name that they used to login to your .htaccess protection.
Hope that helps,