>>huge car hire fees...
That'll be credit hire companies. I underwrote / refused to underwrite a few of these in the 2000's to 2017.
Some were reputable, some were not. All were expensive. Basically a years credit hire would more than pay for the car new. But they have a place and the hirer must be able to show that they needed the car, it was equivalent to the one that they had and one that many seem to forget (and it can be checked) that they couldn't go out and rent the car themselves.
Most insurers / credit hire cos now agree to use the a standard set of daily rates which take in to account the likelihood that not all claims will be paid. Credit terms of well over 500 days are not uncommon.
Most credit hire agreements require the hirer to attend court to help fight the credit hire company's corner if required.
All credit hire agreements allow hire costs to be claimed from the hirer if they are not paid by the 3rd party's insurer. Reputable credit hire companies only use this clause where they have been lied to or where there is clear fraud, not where claims are settled 50/50 etc (the credit hire companies should go through the claim to sense check that the hirer is not at fault). Un-reputable credit hire companies will go after anyone they can.
I used to monitor recovery rates - i.e. hires out to hires paid and they were always disappointing reading, hence the high charges.