Hm. Basically there's a range of conditions where you'd just not ride, where you would now ride with normal winter-caution.
Where roads are gritted, there's no need. A tready tyre is ample. Pick routes to take the main, gritted roads, and the majority of UK conditions are met.
The necessity case puts you up high or up north or car-free in the countryside, away from the gritten track.
The sheer-bloodymindedness case needs no arguing.