This is quite an easy task - just need to get the right access levels.
To delete a staff member as a follower:
You have to be logged on as the user i.e the user must be made active.
The user also needs to have the following access levels - Application / Administration must be 'Settings'.
To remove the instances where they are follower:
1. Go to Settings / Technical / Email / Followers, a list will be given of the documents that the user is a follower on.
2. You may only want to display i.e. 2000 items at a time (when I tried to show 'Unlimited' the system froze / was very slow).
3. Select the items displayed using the checkbox - top left hand side.
4. Using the <More> dropdown menu select 'Delete'
5. Continue until all items have been deleted for that user.
Once this is complete - make the user inactive again.
I tried using import to mass update but it seems like you can only add followers this way, not remove.