I read a while back that impacts below 20mph dont cause whiplash unless of course your in a very old car without headrests.
My younger brother had someone try to claim against him 4 years back, he moved forward and nudged the guy in front and just broke the guys reg plate, him and his passenger got out holding their necks
, (he was doing about 5mph!!)my brother (6'3" 17 stone rugby player) just looked at them and said "dont take the piss lads, my girlfriend is a solicitor and im happy to take you to court for a fraudulent insurance claim", he gave them her card (which we both keep in our cars) and then said "Heres £40 for your number plate, do you want me to call police?", they said no its ok and my bro said, "see you later!".