I have exactly the same issue with my Columbus Sat Nav. Although I'm picking up 10 satellites it doesn't know where I am in the country. Had the system diagnosed by a skoda specialist who said it was working correctly but was due a software update, but this could only be carried out by a dealership. I contacted the local dealership who stated that this would cost me £250 for the update disc. After me shouting at them about what a rip off, they said I was free to contact Skoda UK customer services which I did and they were spectacularly unhelpful!
