The average max daily temperature in December for my location on the southern edge of the Scottish Highlands is 6.4C.
And daily maximums in this area has varied between 10C and 4C most days, with a fair few around the 6C and 7C mark.
So, a fairly average December temperature wise.
It's worth bearing in mind that geographically half of the mainland UK is from Cumbria / North Yorkshire northwards and temperatures here have been much cooler than the rest of the UK.
And as the weather is geographically related, taking the UK as a whole, the temperature has perhaps not been as extreme as many on here are espousing.
Perhaps the really unusual element about this winter is the temperature gradient and weather differences that have existed for so long north or south of the 54 degree latitude line and why there has been so little overlap / change in that position.
Or maybe what I'm really trying to say is that the real question is "why has the 'Euro slug' maintained its position for such a long period of time "