The Carex bronze form is nice - I could have sent you any amount of that a few years ago - it seeds like mad! I'd also suggest the oshimensis Evergold carex. Does well in containers as well as in the ground. Phormiums are superb in containers. They'll give a perfect seaside feel.
Not sure how well it would do in a container, but I have Spartina which is a taller, green/gold variegated grass. I love it but it's not always readily available. It eventually forms a large arching clump.
Festuca Glauca Elijah Blue? Adds a little bit of interest due to the colour
That's the Spartina. The smaller grass in front is Hakonechloa - a lovely grass. Forms a big clump eventually. Neither are evergreen but they start into growth quite early and last well into autumn. Both these plants are quite young.
If you want the genuine seaside product, go for leymus arenarius. It is invasive so keeping it in a container is a good idea.
Thanks! The Leymus does look good, I may have a go at growing it from seed.
It took me two years to get the stuff to grow from seed. The first lot wouldn't germinate.
They did indeed......Thompson and Morgan.