Discovery II Satnav CD

[Zumbruk]

I have a 2002 Discovery which has a factory fit Satnav. It has the original CD in it, which is beginning to show its age. What are my options to replace it? I think the LR dealer wants huge amounts of wonga for a new CD (to the extent it's almost worth buying a newer standalone satnav!) - the built-in one only does the first 5 digits of Postcodes and has the User Interface From Hell). Who makes this satnav? Can I get a s/h slightly newer CD from somewhere - from someone who has replaced theirs with a new one, perhaps? Anyone want to sell their year-old CD? Or are there other, less, er, legal options? Is the data available online, perhaps?