Hi, Inky. I don't think Winter is the best time to try and grow veg in containers. Happy to be told otherwise.
Now I would be growing "grow and cut " salad leaves, not too late to get some mature outdoor tomato plants from garden / plant places. I would sew radishes and put shallots in and harvest them as spring onions. Possibly beetroot.
I've never grown spring cabbage / greens in containers, maybe someone else can advise.
You can grow some long lasting spinach and rocket. Both of mine survived being coverd in snow for weeks, but they were in the garden.
Hope I've helped a little. Good luck.