Thank you for your reply. I started with this and was joined by others a few hours ago. Unfortunately we run in quite a few errors (dmlwriteexception and enrolment button dissapearing) so we are actually quite a bit confused about some Moodle statements, way Moodle calls for things etc.
Currently we stepped off the hiding but went to the simply forbidding for someone that hasn't done Course 1 to do Course 2. Still this system isn't fully in place and we bump into errors.