cat d is just a light bump, just panels, but mostly they are written off due to cost of hire cars for the owner, for example, 1000 quid mondeo, if it was gonna cost 200 quid to fix the car but will take 2 weeks then the policy holder would want a hire car, so if the cost of the hire car is 500 quid for that 2 weeks its over the limit in cost limit on the car, hence it being cat d, id try to avoid cat c's thought unless the repair has been photographed, and cat b and a are real bad, cat b some parts can be used off the car but the car must not go back on the road, cat a, the car must be destroyed or crushed.. hope this helps, mat