Thanks Cathus - that was pretty much what I was thinking. I think the concept is good - just needs some work - or a revisit as I only took 5 frames and managed to crop the right hand edge slightly each time
I've redone the post processing and burnt the sky in a little to give more cloud detail and a pseudo gradient which gives a moodier/stormier feel (by adding a new layer and filling with 50% grey then black brush to burn, white to dodge).
I'm blaming the veeerrrrry naff weather
Cheers
Andy