I do know that most traders do try and avoid cat c/d cars, so when it comes to selling the car you will get less than a non cat car, plus more likely have to sell it yourself.

I rescued a Cat D in 2009.

My intention was to run it to death in a relatively short space of time, which I duly did. This was the pivot of the decision for me as I wasn't intending to keep the car long enough that any botched body work repairs would lead to long term corrosion problems ie, the engine would die before any rust killed the car, and I had no expectation of resale, just scrap value. Worked a treat and when transmission problems started I just got shot.

mate of mine bought a written off car, it had been written off as all the doors were damaged, not a single other thing wrong with it. he managed to source replacement doors from scrap dealers. all together a significant saving over buying a perfect car, although obviously he had the hassle of tracking the doors down and fitting them.