I then checked the licence via Get-SCOMManagementGroup | ft skuforlicense, version, timeofexpiration –a, although found I had to perform a reboot for it to take effect. It can also be verified in the Ops Manager console in Help > About.
I logged onto one of the DC's and created a new GPO, naming it "Local Administrators GPO".
The four "required configuration tasks" that show up on the Operations Manager home screen had now been completed, and three of them had been removed from that home screen. Strangely "Required: import management packs" remained, despite there obviously being a large number of management packs on there, even after a reboot. I considered enabling all MP's just to get rid of this alert, but that seemed a little excessive, and was more likely to create more problems than the fix the this minor issue. There are quite a few minor tweaks I still need to perform so maybe it will sort itself out when I do some of those.