I was once tempted to buy a CAD D - i didnt in the end and bought the same car for 5k more and still wonder if i should have gone for it
I think as long as it passes an inspection AA/RAC and you can get insurance, then it sometimes a good way to buy a car which would normally be out of your price bracket - even more so if you plan to keep it for a long time
No wonder the mileage is so low. I would buy a Cat D personally, not one that is fixed up anyway. Would rather get one that is damaged and have it repaired myself, at least then you know what's happened to it and whether it was just cosmetic damage, etc.