I'm hoping to make it to this one, health willing, as I've been up to Tan Hill on New Year's Day before now, up Arkengarthdale on a touring bike running 25mm rubber.
There wasn't much snow at that point, some time in the early/mid 90's, although we did meet the snow plough coming back down. The driver did inform us that it was rideable to the top, but if we had been in cars he would have told us to forget it!!
We had spent new year at Grinton YHA and the roads weren't too bad, apart from trying to get back up the hill to the hostel from the pub - 25% gradient, with sheet black ice across the road & cattle grid!!