Yup, in December 2010 I saw -14c, 15c and -17c on a car thermometer (as inaccurate as they can be) near Dovedale, not too far from me, on three separate mornings. In contrast, I don't believe it dropped below -10c at the nearest Met Office station in Leek in December 2010. The dales here are really quite steep and narrow compared to most other 'frost hollow' locations and some north-south orientated dales receive no sun until early afternoon in the winter, so I've often seen temperature differences between the tops and dales being as much as 11c on sunny spring mornings. Again, that's according to the car.
There was once a Met Office station further down the valley as I remember the date record being broken on a day in December 2010, the location of the original record being Mayfield, Staffordshire set sometime in the early 20th century. I've got no idea what's happened to the station though.
The nearest frost hollow station is all the way over in Shawbury, Shropshire. I'm quite sure it's often colder in local valleys here, alas we'll never know for sure.