yeah, ive got DAB in my car, Have you got a link to your headunit because that will decide what you need.
sometimes its just an arial
( ive been quoted 40 quid direct from sony for mine as I left the old arial in my old car when i sold it, what a fool)
but its more likely you need the reciever as well, im pretty sure they are quiet pricey, sometimes the same cost as the HU itself. who told you they were a tenner off ebay?