hi Stevet,
as texas said, just had a little brown trouser moment as dvd player/software wouldn't read disc.
spoke to sat nav store, who advised me to try a couple of things.neither worked.
the new disc was fine, followed same procedure, and worked 1st time.
again big thumbs up to them for great service
the worrying bit was getting the disc out, on my 300 there's no eject button on drive, it's in a menu on the screen, which i couldn't get to as it was stuck on the disclaimer!
had to jam the disc to stop it spinning and force an eject, not ideal. (had tried various methods, disconnecting battery, hidden screen buttons)