Having a had a look at the latest trends being picked up by the ECM 12z and now the GFS 18z, it looks as though a complex pattern is evolving at around the 7 day timeframe.
This is based around two areas of high pressure, a blocking high to the NW centred near Greenland and an area of high pressure to the SE over Europe and two areas of low pressure, one out to the SW in the azores and one to the NE up over Northern Scandinavia
How these interact is crucial, obviously affected by the much maligned Shortwaves! The most favoured outcome for coldies is for more of the Southern high pressure to link up with the Greenie high, maintaining an Atlantic block, and allowing Northerly winds to flow down through the country. Conversely, the worst case scenario is for more of the heights to sink south, thus setting up a West based NAO- with winds coming up from the SW as the azores low is allowed to move towards the UK due to a lack of Atlantic blocking.
Obviously, with these kid of setups, the North and East of the country is in the best position as it is closest to any northerly outbreaks that may occur.
Now there is still lots of time for change with this set up and little alterations East or West will have a great impact on whether the UK see's the cold upper 850hpa's move down across the country or whether we are stuck in a somewhat milder set up.
What will probably happen? An evolution somewhere inbetween.
However, the coldie in me wants the Northerly winds to win the battle!