Thought I would add some more info, in Moodle 1.9** I am using 1 table to both create and enrol students.
As above two tables.
PM_ENROLMENT_FILE_17 (table name) AS remote user enrolment table
Col 1 CourseCode AS remote course field e.g. 1L1234
Col 2 LearnerRef AS remote user field e.g. 123456
Col 1 CourseTitle AS new course fullname field e.g. English Language
Col 2 CourseCode AS new course shortname field e.g. 1L1234
Col 3 CourseCode AS new course id number e.g.1L1234
Mappings are as follows
Local course field > idnumber
Local user field > username
Local role field > shortname (I dont match users to roles and all users are assigned the student role)