NezziR said:
What do people call them who are not marines? How would someone such as a planetary governor or a lowly citizen address them?
To actually return to the original question:
In Fall of Damnos the lowly peons start by addressing the normal Ultramarines by "Lord" whereas the sergeant immeadeatly comments: "I am no Lord. I don't rule over anybody." after further discussion they agree to call him simply "sergeant" and call the other troopers by their surnames. Later on several Ultramarines allow the PDF veterans that saved their lives call themselves with first name.
So at least the 2nd company UItramarines don't seem to care much about honorifics.