The bad news is that I've worked out what the problem is. The camera isn't working properly, probably as a result of being dropped that time. There haven't been any obvious problems but I worked out today that it is actually focusing behind the focus point, so to get this shot (which still isn't pin sharp) I've had to put the focus point behind the flower. It sounds complicated, but I know what I mean, just can't explain it very well.
So the camera will be going to the camera hospital and my old camera will be back in use for a while. Hope it's not too expensive - it won't be covered by the guarantee because I dropped it.