Hi Jon, thanks for replying to this.
In my case, I still want the Paypal to work on new courses, I just want it turned off on last years courses - so I don't think the CSS option would work, as would hide the link on all courses.
I did think about the cohort option, but I have a lot of courses to do this on (about 300), and when users access a course, they get 1 year from time of purchase before they are suspended (which paypal handles really nicely), but the cohort option wouldn't. I could download the users, then re-enrol them manually using a csv file, and set an enrolment date individually, but this would be very time consuming, and the learners would get another 'welcome to the course' email, which would be confusing for them, so trying to avoid this.
I expect I won't be the only person in this situation, so wonder if the mechanism could be improved to cover this?