yes you will be able to insure it. It might cost abit more though. My car was vandalised last year and the insurance company were going to write it off. My broker arranged insurance through another company who insures Cat write offs and it wasnt any more expensive. (the insurance company didnt write it off in the end) I dont think you will be able to get away with not telling the insurance company because it will be on the database as a Cat C.
Did you buy the car private? If so, you have no comeback. sorry