OP, you cannot respond to a Notice to Keeper (NtK) as it is not in your name. So what if the hire company sent you a copy of the NtK? What the hire company should have done in order to deflect any comeback to them is transfer liability to you, the Hirer.
Once they have transferred liability, it is then up to APCOA to issue and send a Notice to Hirer (NtH) in your name. Together with that NtH, APCOA are supposed to also include copies of the hire agreement and other documents as listed in
PoFA paragraph 13(2).
Until that happens, you cannot appeal as it is not your name that is on the NtK you have received because you are NOT the registered keeper!!!
So, unless you have received a notice in your name, that is an Nt
H, there is nothing you can or should do.
When you do receive one, then you can appeal with the suggested wording I gave you yesterday.
Either way, even if you did nothing, once the liability has been transferred to the Hirer, all you would need to do is ignore all the useless debt recovery letters and it will eventually go away. APCOA are not litigious.