London Evening Standard are reporting 

Travellers face fines after Heathrow ‘parking scam’

travellers were today warned to be vigilant after almost 300 fines were issued on cars stored without permission by a private parking firm.

The penalties were given out over four days at two car parks run by Hillingdon council.

The town hall’s trading standards team is now investigating whether one firm is using the car parks to store vehicles while the owners are away, read more......