Emma,
I have managed to to setup my Moodle to reflect the diagram very closely.
The keys for me were:
1) Creating sets of courses (Self Enrollment) which will never be accessed directly only via a URL from inside an umbrella course (Manual Enrollment).
2) Disabling the Dashboard completely.
3) From the Front Page only allow Enrolled courses to be visible to the Student/Teacher.
Thank you so much for your help.
Johan