Well, we call our instructor by his first name. [He is 1st Dan]
We dont have any other black belts, so they are called by their first name as well.
When we have visiting instructors, anyone 3rd Dan and above is referred to as Sensei. At Seminars we typically have 3 or 4 Senseis visiting. [Most of them 4th Dan.]
As for Shihan... havent met one yet. [Though technically Tamura would be our Shihan, maybe I will eventually make it to Budapest to see him when he comes... perhaps when I get my black belt.]
Peace
dAlen