Your dealing with Lloyds, whole other story. Since you aren't experienced with insurance work, the overall answer here would take longer than I have at the moment. I wouldn't give them my material prices. Assuming your pricing is reasonable, and within a reasonable range of theirs, I would have the HO tell their insurance to approve the claim and leave you alone. It could boil down to either you want the job at their price or you walk away as well.