Below is some really useful advice regarding clamping etc. This comes from the Consumer Action Group website at http://www.consumeractiongroup.co.uk/forum/parking-traffic-wardens/65341-private-parking-companies-charges.html. Full article below and "Power to the People".
PRIVATE PARKING COMPANIES
A guide to an effective defence.
Firstly the important thing to remember is that Private Parking Companies are not backed by any aspect of criminal law. Tickets from Traffic Wardens working for the police or local authorities or tickets issued by police officers are. There are provisions for them in the Road Traffic Act 1991 and these provisions allow sanctions that the issuing authority can take.
THIS IS NOT THE CASE FOR PRIVATE PARKING COMPANIES.
I'm sure any number of readers will be familiar with such facilities, from your local pay and display to any number of 'multi deck' car parks and even, more recently, the car parks for many stores.
PRIVATE PARKING COMPANIES RELY ON THE LAW OF CONTRACT
And while contract law can be a minefield of offer, acceptance, terms, implied terms and clauses, it can be surprisingly easy to understand in terms of every day matters such as this.
Essentially when a driver of a vehicle drives into a car park and parks his car he is implied to accept the offer for parking on the terms of the offeror (the parking company or land owner). A contract is formed and therefore the contract can be broken (or breached).
The Private Parking Company (PPC) must make the terms clear to the user of the car park. Therefore they are obliged to place ample and appropriate signage about the car park to make those persons using the facilities aware of the terms. The signs must be clear and unambiguous and it cannot be obscured, faded, covered up or in any way difficult or impossible to read and understand. Often times those terms will include a provision that if you over stay you will be penalised to the tune of