If I remember anything from my geography classes at school it is about the Icelandic Low and the Azores High and the fact they produce westerly winds varying from cold and wet to warm and wet depending on the exact locations of these pressure systems. If the Icelandic Low is more to the east or the Azores High more to the west then the resultant airflow across the British isles is more from the north-west, bringing cold wet weather in winter. If the positions of the pressure systems are reversed, i.e. the high is more to the east and the low more to the west then the airflow is more from the south-west bringing warm wet weather in winter.
The current weather chart shows a lovely example of these pressure systems – they are almost exactly north-south of each other – hence a strong, wet westerly airflow.