Typically, Edwardian houses had the most ornate cornice on the ground floor, with less and less detail as you proceed up the house. This is the pattern that I have stuck to.
Our family bathroom had concave quadrant coving. It was quite nicely fitted and made of good solid plaster but not at all in keeping with the look I wanted. I hesitated for a while before replacing it, as it's probably the first thing we've ripped out that was still in good condition, wasn't dated and was only being removed because it simply wasn't my taste, which always seems a bit wasteful to me. At the eleventh hour, I made the decision.....extravagant or otherwise, we were going for the chop!
Our plasterer came in with a team of 4 and had it done in a few of hours.
The bathroom is on the middle floor so we replaced it with a swan-neck cornice. The ground floor will be more detailed and the top floor will have none at all.
Good quality cornice makes a huge difference to a room, I think. Graceful and elegant. Understated period charm.