If you can show me the word "fine" in any of the correspondence you have received, I will not only pay them for you, I will also give you £1,000. Please stop referring to them as "fines". They are not. They are speculative invoices from an unregulated private parking company for an alleged breach of contract with the driver.
As you are in Scotland, you can safely ignore, for now, Horizon and any debt collector letters. Do not engage with them, especially any debt collectors. Do not, under any circumstances identify the driver.
There is no keeper liability in Scotland, for the time being. Only the unknown driver can be liable. Unlike in England and Wales, under some circumstances, the unknown drivers liability can be transferred to the known keeper. There is no legal obligation on the known keeper to identify the unknown driver.
So, for now, in Scotland, you can ignore Horizon or any other PPC as they cannot hold you, the keeper liable. The burden of proof is on the to show who was driving. The only person that can do that for them, is the keeper. Why would you want to do that?
Even if the drivers identity was blabbed, it is unlikely they would initiate a Scottish court "simple procedure" claim. There simply is no money in it for them as a claim for less than £300 does not attract any costs for the claimant if they are successful.