You can buy mini fm transmitters which you can use to reply anything from MP3 to DAB via your car stereo. These are readily available from the likes of Maplin from about £20. The trouble with DAB is not getting it into your car stereo, it's getting a DAB signal sufficiently good to listen to in the first place.
http://www.maplin.co.uk/Search.aspx?...source=15&SD=Y