I'm fairly sure that the concept that you can force a 3rd party insurer to repair at any cost is not fact.
If you can't come to a mutual agreement then it is likely that you will end up in the small claims court. Civil law limits the 3rd party liability at "market value" of the car prior to incident, the reason the write cars off at repair costs of 60-80% of that is by the time courtesy cars and any additional costs in that will equate to market value, so a simple financial call.
They key thing for you now is to establish market value for a similar car based upon pre-incident condition - which is highly likely to be a lot more than the book/trade value!
Do your research, bear in mind at this age condition is key in your search, not colour or even spec..... so you could argue that a clean 4.2 is closer than a shabby 3.7. Find some clean D2's for sale, and prepare to negotiate hard.
If you want to repair your car, then you can ask for a cash settlement or to buy back as salvage, maybe worth considering, but also maybe not depending on your outlook.
Good luck, and glad nobody got hurt
