With you Ian, it's just the humidity that does it, as temps fall towards 0°. Have had Monoblocs ice up pretty solidly quite a few times in snowy/slushy just-above-zero weather, and tis hard to get more than a few miles at a time. Sheer unadulterated misery in fact, as your hands aren't much cop at tinkering at those temperatures at the side of the road. Cold clear -10° dry-air days don't do it. But they freeze your wotsits off just the same.
But hey, it's nearly the shortest day (northern hemi) and we'll celebrate hereabouts with a few hundred classic-bike km next week in the dark/wet/wind/whatever - and then start getting excited like small kids about the return of the light. It's a disease wilko - the apprenticeship never ends and some of us never learn!