Winter salad crops when to harvest?

i am not a natural veg gardener, but this last winter I have grown and overwintered chard, (planted out in Aug/Sept probably, cant quite remember) and a selection of winter hardy salad leaves from the realseedcompany which I sowed, probably a little late, at the end of August.  They're all nice and protected under the cloche/netting but I am a little confused as to when they will be good to eat.  They grew, then halted, and I am wondering if I should have eaten them already even though they are small, or if they will start to bulk up when the weather warms a little.  The leaves are starting to look a bit worse for wear - have I missed the boat?  I've picked some of the chard which is looking good but it's not large and I am reluctant to denude the plants further  Helllp!!!   Thank you!