Speak to http://www.dabonwheels.co.uk - they offer great advice and sell pretty much everything for in car DAB. I have the "digitizor" in my car and a magnetic antenna and it's grand.
It's integrated into the factory fitted radio/cd system (works on one of the fm channels), unit is completely hidden in the boot and system is fed by a very unobtrusive window aerial in the rear side window (I have got an estate). It's operated by a ver small remote control. Reception on it is generally excellent - just the odd blackspot here and there. World of difference from usual AM reception. Very pleased with it.
System was fitted within a couple of days of ordering, by a mobile unit (ie at home). Took about an hour.