Hi Mark,
This is what I actually ended doing. I adjusted my external database course creation tables so that it appends the academic year code to the end of the course id. This way, even if the course code is the same as last year's it will create a new course and new enrolments for the course; thereby suspending all users from last year's course.
The issue I now have is a script which will delete all courses from within a category... but that can wait a bit anyway.
As a slight aside, I must say that the amount of options you have for bulk course actions (i.e. just to move them to another category) and the lack of a "select all" option to be a real pain when preparing for an academic roll-over... If others think that a "select all courses", "deselect all courses" and "delete selected courses" option in "Course and Category Management" would be useful I will put together a Tracker request for an enhancement.
Jon