Just bought 2004 year X5 4.8is which has aftermarket screens in headrests and PS2 professionally installed in rear footwell. All works OK when switched on apart from the fact that I have no sound!!

I did notice that there were some headphone covers in the back of the seats but no actual headphones and nor is there sound when I plug in ipod headphones to the socket in the centre unit.

Any ideas how to get sound? Going on a 200 mile each way trip this weekend so would be nice to sort some sound to put a DVD or two on for the kids in the back.