So from what I can tell from Traveline, these are the changes:
1 increase to every 20 mins, 2 PVR, single
2 decrease to every 60 mins, interwork with 4, 1 PVR, single
3 withdrawn
4 decrease to every 60 mins, route change, interwork with 2, single
6 timetable change, interworks with 7, PVR 2...