I have discovered that I am unable to select street level destinations in a large part of London using either Postcodes or location name. Would be interested to know if this specific to my car or more widespread. If you are using the 2009 Navigation DVD (my A6 was bought new in June 2009) could you try and select your destination as either "High Street" in SW15 or Wimbledon. If I select SW15 on my car I am unable to add the next number in the postcode and Wimbledon simply does not exist, although when actually driving in Wimbledon Nav-Info shows that the roads I am on are in SW15! All very confusing. Do not know if this has always been the case as I have not had cause to go into London much since I got the car.
The car is going into the dealer on Friday and I am hoping the more info I can give them the faster they will sort the problem. May just be that I (and possibly all of you) need a later version of the navigation data.