our 2008 q7 only allows a 5 digit post code which in her job is useless as some of her jobs are farm house's..is there a fix to be able to enter the 7 digit post code 

Hi Andrew.

 Has your satnav been updated? Not sure that your model has this option but most do.

unfortunately the sat nav hasnt been updated but going to buy a new disc and try it 

I presume you have mmi2g high based on the year of the car. Unfortunatly the sat nav is poor with postcodes. There is an soft update to 5577 but that does not help .