When i crashed my car the insuance company knew all about it but in the end I didn't go ahead and claim. I told them i was gonna get it fixed myself and they just closed the case. But they didn't ever see it cos the car was at my parents' farm. Best thing to do is ring them up and ask.
You could buy the car back off them but it wont be worth much when you go to sell it as it was a write off, but if you're going to keep it then that wont matter.
Try and work out how much it'll cost to fix, compared to a claim on your insurance- i.e your excess and the increase in premium and loss of ncb. It might work out cheaper to fix yourself in the long run lol. Insurance is a con