I thought they were just chucked in the ground & left to get on with it. I don't think they're a plant that needs to be faffed about with.
They'll self seed and keep you happy for years to come pulling them out to try & keep them down.
I think you're treated them to kindly. I wouldn't thought with this weather they'd need hardening off, but you could stick them outside for a few days before burying them!
![laugh :lol:](https://chat.allotment-garden.org/Smileys/green/laugh.gif)