Certainly for this area, the BBC forecasted temps do tend to be too high in the winter, mostly at night, but quite often during the day too. Oftentimes, the difference at night can be 6 or even 7C, and what is OK for the towns turns into a proper frost for us.
I watched a BBC forecast today and temps from Mon through Thursday were double figures for here. The MetO 5 day forecast has no temp in double figures for the same time period, they are in the range 8-9C.
In the summer, the forecasted temps seem much more accurate. May be it is easier to get temps more accurate in the summer than the winter?