Thanks for your comments, the lights are from by the site offices. I did do one brief trial the previous night with telephoto end with Ben Dronaig, that certainly demonstrated how the clouds move around the mountain tops.
When the situation is right I'll try another one. At present I'm still experimenting with a frame every 1 / 2 / 5 rates, it will go as far as a frame a day !
I did one at down yesterday which was an hour in 30 seconds similar to the one you viewed. Whilst it was interesting it became more of a solid grey cloud across the sky, so didn't develop into anything worthwhile.
It also needs to be a dry day without too much wind, the camera and tripod (with 10 kilo weight suspended under it) need to be on concrete. My carpet and floor have too much movement, that was the first discovery ;-)
Thanks for your interest.