Over the past two weeks CFS has been persistent in predicting a lot of high pressure over and near to the UK in December, so the cold anomalies could be similar in origin to those that we're seeing right now.
In December that can mean notable frosts and days struggling to get that far above freezing... or persistent Atlantic muck with temperatures stuck at 1-4°C (if the above T2m anomalies were to manifiest), but thankfully the +ve 500mb anomaly near to the UK has trended to higher latitudes lately, although we could in theory see dreary easterlies from that... it's never easy going is it? 
Now, how about those Met Office ensemble mean maps eh Gav?
http://www.metoffice.gov.uk/images/prob_ensemble/20131101/2cat_20131101_temp2m_months24_global_deter_public.png
That 2m anomaly map suggests mid-latitude blocking to me, with stagnated cold the theme of the winter.
http://www.metoffice.gov.uk/images/prob_ensemble/20131101/2cat_20131101_mslp_months24_global_deter_public.png
...and there it is! A very strong signal considering it's covering a 3 month period.
You know, it would only take the ensembles overcooking the polar troughing and we'd be looking at some notable potential for Arctic incursions.
It is a huge shift from the October update though (anomalous Azores high and troughing to our NW... a westerly winter), so that reduces confidence substantially. At least it's a shift a long way in the right direction, and arguably right towards what CFS has been predicting for a month or so.
When you flick ahead to see the 3-5 and 4-6 month predictions, there is a very strong signal for one of the driest winters on record... though the precipitation anomaly maps show only a slight defecit so perhaps some disturbances could find their way to the UK, though they'd have a hard time doing so without being forced south and engaging with cold air... okay now I'm getting carried away 
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2025's Homeland Extremes:
T-Max: 32.0°C 12th Aug | T-Min: -5.4°C 4th Jan | Wettest Day: 31.8 mm 18th Dec | Ice Days: None
Keep Calm and Forecast On