They are hardy, so it's just a question of hardening them off, 'til they're used to life outside the greenhouse.
Give them a week in the cold frame, and then open it a bit, then a bit more, finally stand in a sheltered place for a while - then you should be able to plant them out, I'd aim for the beginning of April
![wink ;)](https://chat.allotment-garden.org/Smileys/green/wink.gif)