Plenty of salad crops can grow outside in winter, with a little protection. In early autumn, the soil is still warm enough to sow seeds direct, while plug plants or seedlings planted out will establish quickly. Make sure you choose hardy varieties of your favourite salad leaves, or you could try and experiment with more unusual crops such as winter purslane and salad burnet.
In summer sow winter salads in shallow rows or seed trays. When they are established plant them out in late summer to autumn, to encourage them to put on growth before winter sets in. Space them at 10cm intervals in rows 20cm apart, and water well. If you have missed the boat and don't have seedlings to plant out, you can usually buy plug plants from garden centres and mail order companies.
For best results, cover plants with a sturdy cloche. The warmer temperature will encourage strong plant growth in autumn, plus protect them from the worst of the weather in winter. To protect them from cold winter winds grow plants in a sheltered, sunny spot. Ensure the soil is free-draining, as plants can freeze if left standing in icy water.