Paul Hudson has produced a copy of the Met Office's previously unseen "cold winter forecast" - the one that was sent to the cabinet office but was not released to the public.
As Hudson notes, this is supposed to represent the average for December-February, so it wouldn't be expected to show the severity of the weather we experienced before Christmas. I'm not clear on whether those are temperatures or anomalies at the bottom.
So it seems as though there was a forecast of cold weather. Assuming that this was what was handed to the Cabinet Office, we then have the mysterious question as to why the Met Office's website at the time was suggesting that it would be warm.
Something to do with Cancun perhaps?
Autonomous Mind's post on the subject is well worth a look too.