I really like V1 Tish. Its really gorgeous. It is underexposed, even though you used +1.
So heres some tips. Bring a flask of soup.
And then... you recognise that this needs +1, because of the sky, but the result is still quite dark; so the likely reason for this, and correct me if I get this wrong, because its really important, is that you used the Exposure Correction adjustment? IF you did, and youre using Manual mode, the EC does nothing. Zilch. Zero. So, being in M mode, and looking at the meter in the viewfinder, or on the LCD, you need to make an exposure adjustment to move that pointer needle over to +1; you do this be either slowing the speed, opening the aperture, or increasing the ISO.
So, its important you confirm or deny my suspicion so I can look at this from another perspective.
I uploaded 3 mods. The first is the image mod. I increased the exposure of the sky area first; and then the water area separately; because they both need different amounts of correction. Using the water area correction for the sky would make the sky too bright.
I cropped a small amount from the bottom.
Correcting the exposure affects the tone. I see you used cloudy, which was the right approach, but you can lose that nice warmth cloudy gives if the exposure is under.
The mod1 is a screen shot from Photoshop, showing your original shot. Its heavily biased to the left, or dark area, with little data extending right, to the bright side. There is some, but what you want is to shift the entire graph to the right, and also increase the HEIGHT of the area on the right. Mod2 shows the image after adjustments, and though the graph is quite similar, they small differences represented in the graph are big differences in the image.
If you want to know the details on how to identify the white point in two different areas of the image, and do the adjustment yourself, I can provide detailed instructions. You need to be familiar with the Threshold adjustment, the Curves or Levels adjustment and layer masking.
The difference in V2 is not white balance, its exposure for those members thinking oherwise!
For Nigel, the exif loaded by the site will always be the exif from the first shot uploaded ONLY. so you cant use it as a reference for any other shot. You would need to nanually include the subsequent settings in your comments.
I hope this is helpful. The modified image shows the great potential in V1, and you can see that gorgeous "peaty" light colour. View the mod LARGE so see it in its full glory. And because its bigger.
Well done, and soon to be better when you answer!