I'm in the cold NEEngland and I cover my earth now with fleece so it warms up quicker. I plant sugar snaps in March as they take the cold. I start lettuce off now so it had a good strength when I transplanted it. Chard also germinate in March. Last year I used nematodes for the slugs and it was quite effective. The ground has to be warm enough but have a look at that. Also Kings seeds have a fair number of cold weather veg that do well for me, that are well described in their catalogue. In the flower stakes I go for Penstemons and asters which stand the autumn well, and keep the colour. If you choose Penstemons with narrow leaves, they stand the cold. Look at Garnet and Firebird.