I am looking to update my 2008 MM1 Sat Nav dvd.

I have come across this supplier
http://navigationdisk.eu/?p=1129#more-1129

Can anybody advise if these are gen Audi discs and has anybody had any previous dealings with them, as they are a lot cheaper that from a Audi dealer?

Are there any alternative suggested suppliers?

What is the position with fitting a dodgy dvd, as it is my understanding that you cannot go back to an earlier version disc, at least not without an expensive visit to your dealer?