Just got 20 small dianthus plugs. What's the best thing to do with them now? I don't have a greenhouse but have a very cold conservatory.
As long as you can prevent them freezing Derek they should be fine. If you can move them away from the windows of your conservatory at night times just as a precaution and put them back on the windowsills during daylight hours.
Derek pot them on into 9cm pots in some gritty compost. They'll be fine in your conservatory over winter. They're hardy so the cold won't bother them much although they will need a degree of protection whilst they're so young. I'd start feeding them some liquid seaweed in early spring and by May they should be ready to plant out.