OMO: I need a (cheap) car, what should I do?

I've been looking around at cars as I have barely used the bike recently, getting into a car and just taking off in the morning is too easy.
So I've come to realise I should perhaps have a cheap runaround. There is car transplants just down the road from me that have some Cat D cars in for £300 and such or I could autotrader a bargain, either way I can get a car for under £500 but when I've been looking at insurance they are wanting £700-800 as all my no claims are on the bike.

So can I (and should I?) move the NCB to a car policy
start earning again and pay the high price
try to put my runaround on my wifes insurance as multicar or something?

Any suggestions greatly appreciated.

Also, Cat D cars, yay or nay? too much hassle or a cheap car if you don't mind the cosmetic stuff (I don't). or are they just impossible to insure.