The danger to much of the country comes from migrating birds, so once they've left in spring, our captive birds could be let loose again.
Another danger is from the import of livestock birds from the continent, so that risk may well not decline at the same time.
However, the last time we had to lock down our birds, it did end in spring so
For deciding how best to work things for your hens, think of the 'five freedoms':
1)Freedom from hunger or thirst by ready access to fresh water and a diet to maintain full health and vigour
2)Freedom from discomfort by providing an appropriate environment including shelter and a comfortable resting area
3)Freedom from pain, injury or disease by prevention or rapid diagnosis and treatment
4)Freedom to express (most) normal behaviour by providing sufficient space, proper facilities and company of the animal's own kind
5)Freedom from fear and distress by ensuring conditions and treatment which avoid mental suffering
So you have to balance 3) against the other points, while ensuring you are also guarding against predators.
We found last time that our hens actually loved spending the winter in our large polytunnel, escaping from their usual battle with snow and rain. They didn't seem to miss the ranging at all. We provide them with vitamin filled alternatives such as peck rings:
https://www.chubbymealworms.co.uk/collections/chicken-treats-1/products/feathers-beaky-fruit-berry-mega-peck-it?variant=20245959737417 and fresh veg and herbs (what's remaining growing in the tunnel) and sometimes a square of turf as even hens do like some grass. Don't forget their dustbath!
