TWR if you read the link this is in the least serious category of driving without due care & attention ( the correct name for careless driving) so it is a maximum 4 points plus a level 'A' fine.
('A' is the lowest level of fine)
On a point referring to this idiots actions, I would advise motorist to be very aware of ice lifting up and blowing off the top of HGV Trailers, the ice builds up overnight when the HGV Is in motion the ice can lift up in long sheets and land on your car, it's a very frightening experience for a motorist and unexpected, if you are aware of this, it will not get you in-guarded, the ice will not damage your car but will shatter on impact.