3 points and a ?60 fine for dangerous / unsuitable use of a vehicle. This relates to anything carried on or in the vehicle that is likely to cause a danger of injury. It covers carrying too many people in a car as well.
You'd obviously have to prove tge danger, a car doing 15 mph on an icy road with 5 inches of snow may not be dangerous but a car doing 70 on a gritted motorway with 3 inches might be.