OP, the links to the PCN have disappeared.
I have never been to that area and really have no idea about the PCN.
As I understand it, you are saying that either:
The vehicle in the video and PCN is not the one hired by you(VRM misread or clone), or
It is the one hired by you and someone else was using it(with or without your permission).
So, if it's 1, this is either because it's a misread of the VRM or the number plate has been cloned. Either of these, and especially the latter, should be brought to Hertz's attention and they should want to know. If it's a misread, then you would want to raise with them why their 'automated system' didn't pick this up. Irresponsible doesn't cover it. If it's a misread then they owe you the money. This is between you and them, let them take the matter to the council.
But if it's a clone(the correct VRM) then you must tell Hertz that there's another car out there. This time flying motorbike, next time armed robbery?
But if 2, then you need to ask yourself how how another person got access to your car. It's still your liability, but you might have someone else to look to for payment.
So actually IMO you need to sort out which of the scenarios fits before you could even contemplate making formal reps.
Is it 1(a), 1(b) or 2?