Hard to know why Trevor. Caused by a circulation change no doubt, but there are so many feedbacks.
As Paul says, maybe not significant in going forward.
Loosely, a cooling in the stratosphere is associated with a strengthening of the circulation in the troposphere, and milder/wetter conditions at the surface.
It is a bit more instructive to look at the zonal mean temp. around 50N as shown in the graphic below.
You can see how variable it gets in the winter months.
The cooling that went on last November did lead to a mild winter in general for the UK.
Nothing much special indicated yet in the forecast on the graph.