Property Damage by Delivery Driver

A delivery van belonging to a large multinational company reversed onto my driveway and knocked over one of my gateposts. The driver got out, inspected the damage, delivered the package to a neighbouring property (not mine), and then drove away without reporting the incident. Fortunately, the entire event was captured on my CCTV system.

I contacted the company directly and was subsequently referred to its claims handling/legal representative. They have accepted that their driver caused the damage, but their settlement offer is only around 40% of the actual cost of replacing the gatepost. They state that this figure has been calculated using an "industry standard" formula.

I obtained a quotation from a reputable local tradesperson reflecting the genuine cost of removing the damaged post and installing a replacement. I submitted this quotation to the claims handler, but they have refused to accept it and will not increase their offer.

Is there anything I can do to challenge this? I have now spent several months trying to resolve an issue that was entirely caused by their driver, and it seems unreasonable that I am expected to invest so much time and effort pursuing fair compensation. I am simply seeking reimbursement for the actual cost of restoring my property to the condition it was in before the incident.