Hey there jamierawr,
there is no GPS problem, my Calais has the GPS button on the screen too, i think its just a factory standard piece for both VE Calais and Calais V GPS fitted or not. the lower class models like the berlina have that button as something different (its in the manual). its an option when bought and if you really wanna pay $3000 for holdens GPS kit go ahead, but i would call you crazy! i suggest get a tom tom or something like that, price well below $200 nowadays, it will give you navigation EXACTLY the same as these factory kits. i think its just the convenience of having the gps built in the vehicle instead of a separate unit that attracts some buyers. me in my opinion see it as useless and waste of money, since ive never even bought a new car after all LOL
the head unit in the VEs dont have a DVD reader in them, the DVD player is in the glovebox. the screen only plays CDs, be nice if it read DVD data disks but oh well i only use the AUX in my iPhone, thats the way to go
if you wanted all the DVD player stuff you should have went for a Calais V, they have the screen in the back and the dvd player...