Not sure about the Leon but yeah mine being a 2006 needs the CAMBUS upgrade as well to make the most of it (and to stop battery drain issue).
I went with www.satnavsystems.com who come to your home and give 3 year warranty. They provide the service to dealers as well - adding nav and other options to the cars themselves rather than getting VW/Audi factory to do it.
Full spec - http://www.satnavsystems.com/main/vw-rns-510-navigation-system/
Thanks for the info (even though I didn't ask for it ). How much is the RNS510 setting you back? Tempted to get it for my Polo but it was horrifically expensive when I spec'd the car.