It's a good time to walk around your plot and make plans as to what you're going to put where etc, dig a hole to see what the soil is like and if it drains ok. If you don't have a heated greenhouse you can start things like broad beans, early peas, onion sets and shallots in pots or divided trays with just a sprinkling of water to set them in but... a sudden cold snap can make beans and peas rot especially if the soil is too wet. If you do have a greenhouse get one of those little zip-up plastic-covered jobbies with two or three shelves, put it inside the greenhouse and stand it on some polystyrene slabs, sow your seeds, zip it up and throw some fleece over it to help keep out the cold. It will need opening from time to time to let in some fresh air and reduce any water vapour. Put a max-min thermometer inside it and another in the actual greenhouse to help you to see what difference in temps there are.