Firstly, how are you claiming? Are you claiming through your own insurer or directly through the at fault party's insurance? You have different entitlements depending on how you make a claim. Your "lawful" entitlement for the loss you have sustained is here :fenchurchlaw.co.uk/coles-v-hetherton-implications-.../

Your best way to claim when it is not your fault, is to claim through an FCA regulated claims management company, or through a solicitor. Claiming through your own insurer or through the other parties insurer directly has it's pros and cons. Through your insurer, you are bound by contract but can complain through the Financial Ombudsman if you're not happy. If you claim through the at fault insurer directly, you have no contract and are not bound by any agreement. They should, but don't always, offer you your full lawful entitlement outlined above. Should things go wrong, you have no entitlement to complain to the FOS when dealing with the at fault insurer directly. The first point to make is do not agree to anything at this point. What is it you want? Do you want your car repairing or for it to be dealt with as total loss if you get the best settlement? Whom ever you are dealing with, ask them for a copy of their engineers report, or "their engineers version of their Audatex report", and if the repair costs are less than the market value, you can insist on it being repaired.