This was at Porthcawl, South Wales. I was working and unable to take a photo. At the top of the shore, among rocks, just below the prom were a couple of clumps of a daisy-type plant. the flowers were purple or lilac with a yellow centre, rather like a Michelmas daisy, but larger (perhaps twice the diameter) and. The leaves were more or less mouse or rabbit-ear shaped, curled inward, and looked rather succulent (not as thick as many succulents but thicker than average). The clumps were probably each a foot or so in diameter.
I can't find pictures of wild daisy type flowers of that colour and wonder if someone can help?
If I can get down there again soon I will try to get a picture.
Thank you. That does look like it, except the lilac colour seemed brighter on the ones I saw. If I manage to get down there again (a lot depends on work and the weather) I will try to look more closely and take a photo.
Here's a picture from http://www.plantlife.org.uk/wild_plants/plant_species/sea_aster/, which does look very like the ones I saw. It seems the flowers are very variable and some even lack to purple rays.
According to another site, http://www.eatweeds.co.uk/ you can even eat the leaves, nicely fried with garlic and butter!