I saw the very light covering on some plants, and cars, for at least the first half of my commute, but not a lot beyond Tooting Bec Common.
We've had big fluffy snowflakes dropping for a while in South Ken, but it's too warm for them to settle, so it's just making the ground damper. The forecast is for the temperatures to just about hit freezing tonight, so there may be some ice. Tomorrow night is forecast to be significantly colder (minimum of -4°C on the Met Office site, -7°C on XCWeather!), so ice is much more likely.
I'm not about to take my Marathon Winters off, the certainty of being able to cycle across anything is worth leaving them on for. I'll review this, and swap over to the Marathon Plus tyres at the weekend, if necessary.