You haven’t specified what the driver did beyond “not paying attention” but if it was a serious enough collision to cause your car to be written off, it could constitute dangerous driving.
(Unless it wasn’t such a big bump but your car was old and the cost of repair outweighed its market value.)
Was he speeding? Did he run a red light? Pull out of a junction without looking.? That could have been a cyclist or pedestrian he hit and not metal.
If police do not attend an accident they can still act on footage sent to them, in fact, some police forces encourage it e.g. West Midlands Police Operation Snap:
www.westmidlands.police.uk/police-forces/west-midlands-police/areas/campaigns/campaigns/operation-snap/
If you see anyone committing driving offences on our roads and it's captured on your dashcam, CCTV or a mobile phone by a passenger, we want you to send it in to us.
It does say:
If you are reporting an incident that involves a collision, please do not use this service. Instead, please call West Midlands Police on 101, select option 1 and provide details within 24 hours of the collision taking place.
If footage has been submitted, it could take weeks before it’s reviewed and for the CPS make a decision over whether to prosecute. If they do, you will be called as a witness. That’s why you shouldn’t take any money from him. Worse case scenario it could be construed as him offering and you accepting payment for favourable testimony to mitigate any penalty. That would be perverting the course of justice.
Your insurance arrangements and how you chose to replace the written off car are not his business and he shouldn’t be involved in it. It may be a kindly gesture to assuage his conscience but you shouldn’t accept any money from him.