Thanks, again for all your comments.
Obviously, I did use CS6 to recover cloud detail and also to colour balance so the sky was the right colour. I had to expose for the sky which somewhat desaturated the colour, at least thats what seems to happen with A7.
I actually have a very nice Lee System 7 filter setup which would have been ideal for this - if only I had had the time to set up a tripod, mount the filters, frame it all up nicely etc etc. As it was I have about three minutes to catch this before is expanded further and began to disperse.
I would add that the small and relatively cheap Leica C-40 Summicron is a fabulous lens for the A7. No smearing as far as I can tell, very sharp stopped down and it seems to draw beautifully with the A7 sensor. Interesting match when you consider that about 40 years separates the technology!
LouisB