Don't let the insurance company take you for a ride on this. You don't have to do what they say. All the crap about cat this and cat that is all rubbish it's your vehicle and all the decisions about it are yours,, the categories only come into play when they have taken ownership of the vehicle and not before. You are the owner of the vehicle and you make the decisions.
Consider this if your vehicle was insured third party, you would have had to pay for it's recovery and it would be parked on your drive in all its wrecked glory. It would not be recorded as any sort of "write off" or appear on any data base and you would be free to do what you want with the wreck, repair it, restore it, break it for spare,. whatever your hearts desire and it would not be recorded on any stupid insurance data base or anywhere else. don't let the bastids take you for a mug, you insist on what you want and don't let 'em take the ****.
It's still your vehicle despite what the insurance companies will say and you make the decisions.