Thanks for the informative reply. The date on the photos is 7th July 2012. The first one was taken at 15.00 and the second at 17.30, near Great Dunmow, Essex.
I think it was a stormy day with plenty of cloud convection. When I took the first street shot there was lots of mamatus cloud right overhead and the sky was a strange colour.
With the second [field] shot, we sometimes see big convective clouds forming across the ridge line, and sometimes a line of them in summer - it can be quite spectacular - I've attached a couple of examples.
That area seems to act as a "seed" area for clouds.