Let's be clear on this as it will not be the first time that a lease company manages to screw this up and leave you out of pocket.
You cannot do anything until you receive a Notice in YOUR name. You will note that the copy of the Notice to Keeper (NtK) that was sent to the Registered Keeper (RK) Mitsubishi/Hitachi or whoever they are this week, does not comply with the BPA/IPC Private Parking Single Code of Practice (PPSCoP) section 8.4.3 which states:
"Parking operators must provide a process for rental and leasing companies to transfer liability."
Missing is the required information for a Lease/Hire company on what to do if the vehicle is under a Hire/Lease agreement. It should mention somewhere on the NtK something along these lines:
"If you are a vehicle-hire firm and the vehicle was on hire at the time of the parking incident, please let us know and provide us with a copy of the hire agreement and a copy of a statement of liability signed by the hirer under that hire agreement."
The NtK does not have any statement informing rental and leasing companies on what they must to in order to transfer liability. If the lease/hire company transfers liability as required by PoFA, the operator cannot later go back and try and recover anything from them.
Mitsubishi's letter of the 15th March says they have transferred liability to you. However, unless they have done so in accordance with the requirements in PoFA, technically, they can still be liable. They were required to send to the operator copies of:
(a) a statement signed by or on behalf of the vehicle-hire firm to the effect that at the material time the vehicle was hired to a named person under a hire agreement; (done)
(b) a copy of the hire agreement; and (???)
(c) a copy of a statement of liability signed by the hirer under that hire agreement. (???)
They have complied with (a) above but have they complied with (b) and (c)?
The operator now has to issue a Notice to Hirer (NtH) in your name and should include with that NtH, copies of the documents mentioned in (a), (b) and (c) above together with a copy of the NtK that was sent to the RK. IN 99.99% of cases, the operator fails to send copies of the required documents as stipulated in PoFA paragraph 14(2)(a) which means that the Hirer cannot be liable. Only the driver is liable and they do not know the identity of the driver unless you, the Hirer tells them, inadvertently or otherwise. So, you must only ever refer to the driver in the third person. No "I did this or that" only "the driver did this or that".
For now, you can not do anything until you receive the NtH in your own name. When you do, then you can use the appeal as provided above by
@DWMB2.