You appear to be reading a lot of out of date web links, Secsee1!
Where a private parking company (or, say, a church or community centre) clearly displays notices stating that users of their car park must pay a fee for parking (or for parking beyond a specified time), then any driver parking there automatically enters into a LEGALLY-BINDING (and fully enforceable) CONTRACT to pay such fees. That has been tested all of the way up to the highest court in the land:
http://www.legalcheek.com/2015/11/fish-chip-shop-owner-who-refused-to-accept-parking-fine-changes-contract-law/
At one time it was correct to say that only the driver of a vehicle could be pursued through the courts for non-payment of such a charge, and not the registered keeper. However when the Government announced plans to ban wheel-clamping, car park owners and operators pointed out that they would then be left powerless to deal with unauthorised parking. (e.g. a supermarket close to a football ground could find all of its spaces filled by supporters on match days, costing them vast amounts of money in lost trade because genuine customers had nowhere to park). So when the Protection of Freedoms Act 2012 came into force, which banned wheel-clamping, it also gave car park operators the right to pursue the registered keepers of vehicles for unpaid car parking charges when the identity of the driver couldn't be established.
http://www.legislation.gov.uk/ukpga/2012/9/schedule/4/enacted
To be enforceable in law, parking charges must be 'not unreasonable'. The Penalty Charge levied for dropping off a passenger at an ordinary bus stop (marked with a solid yellow line, indicating 'No Stopping') is typically £70, so it's highly unlikely that the figures you quote would be regarded as 'unreasonable' by any court.