I'd agree that you certainly don't need flaps for an ILS in a 172. They are plenty draggy enough to lose lots of speed even going downhill from 250' agl. Not having the flaps down also means less configuration change for a go-around.
I did my IR in a 172, and the SOP (from fading memory) was to use about 100 kts flapless on the GS. I can't remember what power settings gave that, though.