Ummkay....managed to figure this one out for myself and thought I might as well post a follow-up in case anyone else wanted to do it in the future.
Bring up /etc/e-smith/templates/etc/httpd/conf/httpd.conf/95ApacheMP310Handler in vi and on change line 33 to look like this:-
$OUT .= " PerlSetVar SortField track,title\n";
This will now sort the directories by track number first, then track title. Altogether much better for directories with albums in them.
Do a quick '/sbin/e-smith/signal-event console-save' to rebuild your config files and you should be laughing...
Gary