I've just learned, from a post on Facebook, what to do it you see a sheep lying on its back. I checked it out (on a couple of farming sites) of course and now feel I am a better citizens for it. Thanks Facebook.
I saw that too! It was news to me, and I lived in the Welsh mountains for 4 years. Every day a learning day:)

A ewe late in pregnancy is a very unwieldy beast, and if they stuck on their backs the crows and foxes will move in very quickly - frequently within a couple of hours. If you don't get to them quickly they can be in a right mess. Even if they don't get pecked/worried they can develop very bad pressure sores very quickly and the pressure on their internal organs does them no good either. I have pictures, but you wouldn't want to see them.
If you see a sheep on its back, never be worried about the right way to get them up, roll them over any way you can and steady them whilst they get to their feet. They can be a bit wobbly at first, but they soon recover.