Brassicas monkeys...

Mine are still only seedlings

Brassicas are hardy things, so should be OK, but they won't take kindly to being planted out if they haven't been hardened off (put out during the day, brought in at night, for a week or so)

I also think that plants that are restricted at the root suffer ... so if in any doubt my suggestion would be to pot them on to pot that are 1.5" bigger diameter than the size of their current module cell - and that will buy you two or three weeks before their roots fill that and they have to go out - nothing to stop you planting out earlier than that once they are hardened off (although if the roots haven't filled the pot the rootballs will be a bit inclined to fall to bits as knock them out of the pot to plant!)

Thanks guys.

Started hardening off this week, will pot on and continue hardening off.