In reply to Kryank:
Weird. It looks like a warm front pushing into cooler air from the left, which if the photo was taken in the morning looks like it might be north/north-west. The warm air is pushed up making the ragged cloud front.
The opposite to a sea-breeze front, sorta.
Hopefully some meteorologist will be along shortly to tell me where I've gone wrong
The ones in BNN's lovely pic are lenticular.