What happened when you complained to PPM about them failing to manage the parking and them "renting" out your allocated space to an "unauthorised" vehicle? What did the managing agent of the property say when you did likewise?
Terrible signs. You need to have a read of your tenancy agreement/lease and note what it says or doesn't say about parking. PPM are allowing anyone to park in your space as long as they agree to pay £100 for the privilege.
The signage also breaches the IPC CoP, the CRA 2015 and invalidates their ability to rely on PoFA 2012.
PoFA 2(2) and 2(3)(b)(i) and (ii) are not satisfied as those signs fail to provide "adequate notice" of the parking charge, and fail to bring the charge to the notice of drivers who park vehicles on the relevant land. However, you may have thrown the ability to rely on using that as it would appear you have admitted to being the driver.
https://www.legislation.gov.uk/ukpga/2012/9/schedule/4/enactedIPC CoP v9 Schedule 1 states: "The size of the text on the sign must be appropriate for the location of the sign and should be clearly readable by a Motorist having regard to the likely position of the Motorist in relation to the sign." This suggests that the readability of the text is a key consideration, particularly from the perspective of someone inside a vehicle.
This means that the text on the sign should be sized and positioned in such a way that it can be easily read and understood by a
motorist while they are
in their vehicle, considering where they are likely to be in relation to the sign. In other words, the text should be visible and comprehensible from the typical vantage points of a
motorist approaching, passing by, or parking near the sign.
https://irp.cdn-website.com/262226a6/files/uploaded/IPC%20Code%20of%20PracticeV9%20V4.pdfAs far as the CRA is concerned, there are several abuses of the Act. However, at this initial stage, they are not likely to even be considered by PPM. Some of the CRA breaches will require reference to the landowner contract with PPM. For now, CRA 49, 50, 54, 55, 62, 63, 67, 68 and 69 apply.
In simple terms, those signs tell anyone able to read them that PPM have the right to rent out your demised parking space for the sum of £100. For example the owner of a very expensive car could decide that they can park their vehicle in your space, away from the public road, for the discounted sum of £60 if they pay the charge within 40 days of receiving the notice.
https://www.legislation.gov.uk/ukpga/2015/15/contents/enactedThere may also be a defence that the lease has supremacy of contract, especially if the landowner or their agents failed to adhere to the requirement of The Landlord & Tenant Act 1987 Section 37. This would need to be assessed against the master lease.
https://www.legislation.gov.uk/ukpga/1987/31/section/37 Unfortunately, you are dealing with an unregulated private parking company and the IPC. As long as you feel aggrieved enough about this injustice, you are most likely going to have to wait until this goes to court. PPC and the IPC are likely to ignore all the arguments above as they are basically a cabal of ex-clampers who rely on their victims capitulating under the pressure of their threat tactics.
For now, Plan A, a complaint to the Managing Agent or the landowner is your first port of call. Plans B and C, appeals to PPM and the IPCs IAS would be next but don't hold your breath for ay positive results from those. Plan D, going to court and letting a judge decide whether you owe PPM a debt or not is the most likely way that you would see this off. Many of these shyster firms will often discontinue before it ever reaches a judge, knowing that they are likely to have a hard time justifying their claim if it is robustly defended. They just hope that their victim is going to capitulate once they receive a county court claim.