PV, all those plants have similar requirements.
They are very drought tolerant and do not require constant moisture. If they are still small, you can put them all together for now.

I still have a bunch of perennial seedlings to plant out.
I put them in small individual pots to get them ready for a plant sale next year.
But I am contemplating re-potting them in larger containers because they have grown larger and their roots seem confined.

I think I'd plant or pot the sea holly individually rather than combine them in a communal pot. Of those you list, the sea holly will transplant from a large combined container the least successfully, they form a tap root that can be easy to break without care.

Thank you both! My original plan had been to plant the sea holly and rose campion together; I'll place those where they won't be too disturbed when I take the others out next year. The pot has been sitting waiting for them for almost two months now, but it's just been too HOT and I couldn't deal. So, today's the day!

Thanks again ....

PV