"Non-State" covers the other airfields. All centres are NATS controlled, as are most of the major airports. At other airfields the local authority employs ATC staff. For potential controllers some have their own training schemes where they pay for staff to be trained by NATS. I don't know the current ruling on what is required before applying for an ATC licence but in the past it has been posible to undergo training with a supervisory controller and do one's own study prior to sitting the licence exams.