I brought my adaptor last week and for the 1st couple of days the buttons on my steering wheel stopped working (whether or not that was to do with the adaptor I don't know). Then all the buttons started working again and for 2-3 days I had no problems but then today it says no media found. I have tried disconnecting it then reconnecting it, turning the ipod off then back on, switching the car off and on and even trying a different ipod but nothing is working 

Does anyone know what could be causing this and how to solve it 

Could need a full 'reboot' of the B&M happens from time to time, try Merlot's suggestion first as it resets the internal library file that can get corrupted at times (4-5 mp3s on a stick doest the job). If not, wait until the ignition has been off for 5 minutes, pop the bonnet and disconnect the -ve battery terminal (easy with the quick release mechanism) for about 15-20 minutes, reconnect, worth noting you will lose all trip data and need to reset the clock.

Pretty much, it allows it to do things like random play and remember where it was so you can skip backwards and forwards even if it was in random mode.