On entering the car park you agreed to abide by their terms so it is legal but more a matter of breach of contract, as mdoo98 suggests take a look on moneysavingexpert.
http://www.moneysavin...ivate-parking-tickets
Would point out however that technically as you'd left the vehicle in order to meet your wife you weren't waiting but parked.
The DVLA would have provided your address details and unless you're exdirectory probably a few minutes work for a bailiff company to get your telephone number.