Cat D is not necessarily a bad thing, granted you'll have to do your homework as to what repairs the car required and what the quality of that work was. Provided it's a big saving I'd consider it, but as mentioned you'll need to price accordingly when you come to sell it yourself and expect a lot of questions asked by the buyer.
But as some of the guys have mentioned there a lots of non Cat D cars out there. But then if your budget is tight and it allows you to get the car you want then fine.
It being Cat D only shows that somebody declared the accident to their insurer, there will be plenty of non Cat D cars out there that the owner just had repaired themselves to avoid an insurance claim. Bosh a secondhand wing on, lights and front clip of ebay and sell it on.
