Those signs are not capable of forming any contract with the driver. The headline terms are purely prohibitory: “Permit Holders Only / This area is for the use of permit holders only”.
That wording makes no offer to non-permit holders capable of acceptance. Without an offer, there’s no contract; at most there could be trespass, which only the landowner (not the parking operator) can pursue.
The sign requires a prior arrangement (“report to the management office… to obtain a permit”). That confirms parking is pre-authorised only. A driver arriving without a permit has no mechanism to accept terms there and then, so a £100 “charge for breach” cannot arise by contract with them.
The detailed text is in very small print. Even if an offer were intended to non-permit holders, the core terms are not prominently conveyed to that class of driver; the dominant message is prohibition.
For permit-holders, the sign may operate as regulatory signage supplementing the separate permit agreement (e.g., “park within marked bays”, “no yellow lines/hatched areas”). Any contractual relationship would arise primarily from the permit’s terms, not from this sign.
Conclusion: The signage is incapable of forming a contract with non-permit holders; any purported £100 “parking charge” against them is misconceived. It may regulate permit-holders under their existing permit terms, but it does not create a freestanding contract with non-permit holders.