vosa will not "un write it off"
if its a cat c it will need a vic check, which is a chassis number and a engine number check, and thats it
you will also not need to buy it back if its of cheap value, they should just keave it to you to dispose of, asling to buy it back from the start is great in there eyes as they just reduce for it. say noting until they make an offer, before you accept just ask them what happoens to your old car can i keep it