I have checked the menu settings,they are ok, the disc is a 2016 disc and at £152 a pop i wont be replacing it again for a while.
as you say the head unit is also expensive,i have been toying with the idea of checking all the fuses in the cabin,i don't know if the voice would be on a separate small fuse
of its own. I suppose anything is worth a try.
thanks gents for your thoughts.