Ok all, thanks for steering me in the right direction. It seems the default "creative style" settings for "standard" in the manual settings is with the saturation & contrast set to the negatives. A few minor tweaks has made all the difference and my photos no longer look washed out. So ends months of frustration. If only I'd asked sooner!

Yes, I think your right. I repeated the experiment with some variations with much the same results. It still bugs me though that despite my best efforts and research I still can't take as good as photo as the camera can when I switch to manual settings.

The 4 photos that I posted are just to illustrate the problem I seem to be continually encountering. I repeated the settings that the camera chose for the first shot in full Auto mode. These were:
ISO 100
f/11
1/160
The camera is a Sony SLT 30a
The lens used was a Tamaron 17mm-50mm f/2.8 but it doesn't seem to matter what lens I use. Auto mode photos are often superior to those shot in P, A, S or M mode.

Just to clarify, picture #1 is with the camera in full auto, not just auto white balance.
I don't really wont to go through life photographing everything in Auto mode but it seems to give a better result than me adjusting the settings.

It seems that I often take a better photo with the camera on Auto rather than trying to control of the settings myself. I'm thinking it has to do with White Balance. The four photos below are all taken with the same settings. The first one is with the camera on Auto. The second with the WB set to Daylight. The third with the WB set on Shade and the fourth set to Cloud. As you can see Auto has a lot better colour and is better than the other three. So do I need to do custom WB for every photo or what?

Auto


Daylight


Shade


Cloud