ok gotcha. I do think though that the channels solution is the better one.
If you open both your 1st derwentwater image and your second in photoshop, compare the histograms. in the first, you see a peak off the top on the left side (shadow detail loss), on the second, you see more data loss on the right of the image (more blown snow than the first one).
If you open the first image again, then look at the histogram and the layers palette, click background and you see the channels below in the box, rgb, then red, green, blue. click the red channel, the image goes a water grey/black/white. then to to image, calculations. a box pops up. makes sure that red is selcted in the channels box in both boxes, then choose multiply. at the bottom, pick "new channel". you 'll see this
this creates an alpha channel. its a seperation of the red elements of the image (the brighter the bits in it, the more red. blow outs and skin etc is always the red.
so, now go to image calculations again, and when the box pops up you ll see its darker again, like this
this is further isolating the problem areas. at the bottom of the box where it says "result" click the drop down and choose "selection". you ll see a broken line around the snow on the hill, and the reflection on the water. then click rgb in the layers palette, then hit the option button on it (the half moon black white circle) and choose curves. a new box pops up and you can drag the curve up from the middle to lift all the white areas (the hill snow will be affected too, but fear not). When you do this it does it in proportion. all the shapes are maintained and you are ONLY affecting the red areas from the channel. so now what you see is a big lift all over, which is causing more blow out on the hill. so..
hit the wing menu (three small lines, top right of the layers palette) and choose "new group from layers" - a box pops up which says group one. ok that. then hold down the alt key, and press the square with a circle in it in your layers pallette. this creates a layer mask, and you see a little black box pop up in the palette. making sure you select white on the left hand side colour choice (the two squares overlapping on the left of screen ), then pick brush, whatever size you want, and brush over the areas you want to lighten (make sure your opacity is set to 100%).
you ll see immediately that this brightens the snow and reflection whereever you brush. it wont brighten dark areas, only bright and pale-ish.
If you then want to do this with the dark areas, just do it again using the same alpha channel you already set up, but when the calculation box pops up, tick the "invert" boxes - all the white areas are the dark areas and the ones youre going to change. choose selection and go the same with a curve layer.
the contrast is sorted out via the green channel. i ll tell you how to do that if you want. anyway, the end result i get is
if you download that and open it, check the histogram now, and compare it to the original. all this is irrelevant if youre not going to print it by the way, but if you are, you ll need to sort out the blow outs in the right way.
hope that helps, and let me know if you want me to tell you how to do contract correctly (ie not by just using curves or the contrast slider)
by the way, the banding see in the sky is due to the low res image, it wouldnt do that on the high res