You write and tell Octopus Electric Vehicles to stop being such feckwitted eejits and to actually read PoFA paragraph 13. Then explain that as long as they have followed the wording of the legislation, there is no way that they can be held liable for the charge.
To paraphrase paragrap13: If, within 28 days of receiving the Notice to Keeper (NtK) they provide the parking operator copies of a statement to the effect that the vehicle was hired to a named person under a hire agreement, a copy of the hire agreement and a copy of a statement of liability signed by the hirer under that hire agreement, then the parking operator CANNOT exercise their right to recover from the Registered Keeper the amount of the charge.
In other words, as long as they do the above, there is no comeback on them and liability is transferred to you, the Hirer, not the driver, as neither the lease company nor the parking operator have any idea who the driver was unless you, the Hirer, blab it to them, inadvertently or otherwise.
If they are unable to figure that out, then they only have themselves to blame for their own stupidity and you can chargeback anything they try to take from you for their own mistakes.