We are in the coldest patch we have had all winter and I’m still able to harvest from my plants. Today we’ve enjoyed the (small!) aubergine that was on the plant we have kept on the windowsill and a fennel plant from the back garden (also not massive but unlikely to grow any more).
Of course, when I ventured out after dark to collect the fennel I was soon reminded that one of the reasons for limited winter harvests is when the ground is frozen! Fortunately I only had to free up a couple of inches before I could pull it free.