I think that what you are trying to center is very evident. The focus showing the detail on the leaves are great. The blurred back ground really adds to what you were trying to show. Great job.
I"m not really clear on what's centered about this photo. Also, the flower petals don't seem very sharp, and the white on the back top is a little distracting. Keep at it!
The white space in the background is visually distracting. You could have cropped it and still kept the bluebells centered (except for perhaps the most dogmatic voters).
Lovely shot, nice dof. In this situation I might have picked the leaf that is casting the shadow on the front two (center) flowers. It is somewhat distracting and the shadow it casts is blocking the detail that we may otherwise see in the center of the picture. Good shot.
I realize one could argue that this one in fact is centered, but I do get the feeling that it isn't. The blue bells catching the eye is way out of it and also not surrounding the center which would have helped out. On my TFT it looks a bit over-sharpened, something I manage to do a lot to my own images on my other (CRT) monitor. Skipping that last USM seems to be a good idea sometimes. It's nothing I'd take points off for, just a possibly useful hint.