Regarding the answers above, my experience with insurance companies falls between both Glos and RW.
I have had a car that was 15 months old stolen and my daughter was involved in an accident where her 9 month old car was declared a write off.
With my car, the insurance company simply looked at the value of my car at its age and mileage and offered a settlement based on that, irregardless of extras or its previous condition. As it was, I couldn’t find similar at their offer.
My daughters insurance company offered like for like in the first year so they went to her dealer and got a copy of every extra and ordered a brand new like for like.
Companies are different and can’t remember which they were as I changed every year but I always used big name companies so ‘decent’ is subjective!