As this incident is not your fault, your lawful entitlement is here: fenchurchlaw.co.uk/coles-v-hetherton-implications-.../. As long as the repair cost are less than the market value, you can insist on the vehicle being repaired. With repair costs at £1800, it will be a total loss as I doubt your car is worth more unless it's high spec and low miles. Your insurance covers you "up to" the market value of your car. If the repair cost are more, then unfortunately your car is a total loss and you will have to accept that fact. What you do not have to accept is the market value offered, check in the marketplace to make sure the settlement is reasonable. You're also entitled to an alternative vehicle until which point settlement is agreed. A reasonable time should be given in the interim to source another vehicle.