To take the computer out of Managed Mode, whilst logged on as administrator run the command below on the client computer.
You will need to ‘CD’ to the McAfee folder path which includes the frminst.exe before running the command
frminst.exe /remove=agent
If you wish to uninstall the agent after running the above command, type the command below or just remove the agent from Add/Remove programs.
frminst.exe /forceuninstall
Worked like a charm, thanks