P&OC... Not my area, but I've got some great colleagues in that team, worked very closely with P&OC people for the past 8/9 months or so now, good bunch of people.
If you made manager in 12 months, starting from the 60k offer you currently hold. Yes, I would expect something around 67-75. However There are managers who make slightly less, although these are the managers who maybe hold a slightly lower SC salary than you have been offered, as I have said, a 23-26 year old SC may only be on around 40-42k, with a 3 year progession to manager they would be very lucky to be looking at 75k, more likely around the 60mark. Hope that makes sense, bit of a brain dump.