Guys - this one was covered on Watchdog last week -here's some advice:
1. Private firms who are members of the British Car Parking Association have access to DVLA records, hence the traceability
2. You do NOT have to pay fines they impose - even if they threaten.
http://www.bbc.co.uk/consumer/tv_and_radio/wat chdog/reports/transport/transport_20080225.sht ml
This from the article: Conrad Murray is a lawyer who thinks the public are frightened into paying up when they receive these charges from private firms. Unlike penalty charges from the police or councils, you�re not legally obliged to pay them. He says that if they charge is unreasonable you shouldn�t pay, �If you get a parking charge notice you haven�t broken the law; you�ve committed no offence.�