Hydroponics is your answer.
I grow a few plants over the winter, or at least allow hardy enough veg to stand in the ground.
Many brassicas are ideal for UK winters, as they can go dormant in the winter and "wake-up" in the spring.
I've leeks, Brussels sprouts, kale (borecole) winter onions, beetroot, and swedes already growing for winter, I have 2nd crop potatoes, more beetroot, lettuce and more winter onions in the polytunnel, and I'm about to sow pak (bok) choi, cauliflowers, broccoli, cabbages and the garlic goes in about 3 weeks from now.
I'm also digging in shredded tree branches and another 3 1/2 ton load of cattle manure to the ground, in preparation for next year.
If you consider that I'm still harvesting beans, peas, courgettes pumpkins, cucumbers tomatoes, lettuce, summer cabbage, aubergines, and hopefully my sweetcorn will beat the frosts, it's a busy, busy time.