After much fiddling around:
The first challenge was to lighten the picture without making it look too washed out - the curves tool proved invaluable here. After I had done that, I realised that there were people in the picture! I decided to crop to a 16:9 format and did some work (in a rather hasty fashion) to make the people more visible.
I also boosted the colours a bit using the channel mixer and added a very subtle blue to white gradient layer, set to "darken only" mode and turned down to be barely visible but add just a touch of depth to the sky.
A better exposed picture would make a much stronger starting point but this could work as a reasonable rescue (especially if I had started work on a larger original and applied my sharpening after resizing to fit the 600px limit
).
Wulf