If you are lucky to have a greenhouse, even an unheated one, you can try to force some herb for an early crop. Some herbs like mint and chive are ideal for this treatment. Dig up the roots in late autumn to early winter, divide and replant in a peaty growing medium in large pots. You can also try with tarragon but it will need some heat to bring it on early.
Plant trees, bare-rooted roses and hedges during their dormant period. Also you can start planting garlic bulbs.
Clean and repair all your garden tools and equipments. Thoroughly wash and clean the pots, seed trays and any equipment needed for propagation, getting rid of scum and tidemarks. Clean out the greenhouse, wash the glass and make sure to not leave any old bags of potting compost around to harbor pests and diseases. Oil and clean garden tools and equipments to have them ready for the season to come.
If the weather is not too severe you can try some building projects in your garden like laying new paths, terraces or hard surface areas. Also you can lay out new garden schemes and have your beds prepared for planting.
Herbs in containers
If you have not put all your pots under cover you have to protect terracotta and stone pots against severe temperatures by wrapping them in fleece or hessian. Roots of even the most hardy plants are more vulnerable if grown in containers and if the soil freezes it will expand and crack the pot.
For herbs that were brought under cover over the winter provide a minimum watering, just enough to ensure the compost does not dry out completely. Do not feed any of these plants.
Check that outdoor-grown perennials which are not totally hardy, such as lemon verbena, are adequately protected with fleece. Some of the ornamental thymes will also benefit greatly from a light covering as they dislike cold winter winds and waterlogged roots.