This is one of the things that vexes me with insurance companies, but with misinterpretation I've found that if you ultimately speak to the right person, common sense prevails. If not, a mention of the Ombudsman helps, if something seems so blatantly unfair. When someone caught a (rusty) front wing on my parked 88 300CE whilst parking himself (my wife had just parked), I was able to persuade his insurer, armed with the price of a genuine new one, that a replacement was probably as cheap as the labour etc. to repair the damage he had caused. They phoned me back to agree. I don't know how a bonnet would compare price wise, but worth a try, and I wouldn't carry out any work until instructed and agreed by the insurer. Good luck for pain free outcome.