I also use a P300, and have experimented with it's in-camera HDR mode, while I believe you took separate images, and later used software to combine them in a single HDR image. Am I right? This is obviously the best way to produce HDR images, but the question needs to be asked whether any camera's HDR modes are worth using.
I have used the P300 HDR mode, where you press the take a picture button, and in a short period of time, less than a second, an hourglass appears, which stays there for several seconds, and then you see the result.
The first time I tried this, the results were not good, but I was hand holding the camera, and the combining the camera did wasn't very good.
But I tried another time where I put the camera on a flat surface, and where I believe it kept the camera much more still than if it was being held out in front of me with no viewfinder available, and the results were better.
The camera provides 2 pictures from this mode, one which looks like the result of normal camera metering, and the other that is the HDR image. I had to increase darkness and contrast on the HDR result, and I might have then reduced saturation a bit. I ended up with a photo I quite like.
The P300 doesn't get much respect, but I think that in the right level of light, it is a tiny Jpeg gem.