Late to the party, again, but your only option really is to remove the factory stereo and fit a standard CD player with DAB (if you really want that). There will be a how to on YouTube I expect, you'll just need to buy your desired stereo (will probably be IRO £50 - £80), and the relevant wiring harness adaptor that plugs from your factory stereo wires into the new stereo. If your factory stereo is a double din (i.e. takes up two shelves) you'll be left with a gap which you can just fit a plastic tray into.
Pictures of your car would help, as if the stereo is all integrated into the dash I will be a lot harder or not possible.