With regards to the jobsworth taking down your number plates, you'll just get a letter from the police saying your vehicle has been seen driving in a certain manner and has been reported to them.
I performed a perfectl legal overtake on some bint doing 20mph down a 60mph country road. 2-3 miles later, I see her come flying up behind me flashing her lights. She then followed me for a mile or so, at which point I stopped the car and got out to ask what her problem was. She said I nearly killed her and her baby by speeding past her (i was driving a 99bhp 1.0 focus) and she was going to report me to the police.
The funny thing is she must have been doing silly speeds to catch me up. I laughed in her face when she didn't have an answer for that. Silly slag.