The link you have provided doesn't work for me, it links to a private Facebook group of which I'm not a member.
Let's see the original notice you received, your response, and any subsequent response from the parking company. It'd also be useful to see photos of the signs in the car park. You may need to use a 3rd party site like Imgur to upload photos.
The IAS are fairly unlikely to accept your appeal - your best bet here will be to speak to your employer about the matter. If you're in a trade union, see if your rep will support.
