I was driving back to London up the M4 today and outside Reading there are roadworks with narrow lanes and a 50pmh speed limit. I was in the outside lane and everyone was going at the speed limit so moving reasonably fast. The car in front of me kept crossing over the dotted line into the lane on their left which was a bit alarming. Then the passenger in the back seat hung halfway out of the window and handed something (I think it was a lighter) to the driver of another car in the middle lane
I had to stop for petrol at the next service station so wrote down the registration numbers of the cars. Should I report them and would the police do anything or do they have to witness reckless driving?