The real benefit of using original locked img files is that you probably know where they've been [hopefully nowhere bad]. Remember what your Mum said to you as a kid about that thing you picked up? Same principal really. Newbies like unlocked images because they think they're 'easy' ..... until a corrupt img bricks their unit that is. And unfortunately they're exactly the ppl who then don't know what to do about it.

Your EU fw units cannot use any detail map 'unlocked' with a JM code as dasilvarsa said. The GMA protection is still there so they'll be 'unauthenticated' on the unit which is as good as locked anyway.

Best advice: If you want a already compiled image, dl a locked one and unlock it yourself with [Only registered and activated users can see links. ]. If you want to be even more careful, dl a locked gmap folder and make your own image with BaseCamp/MapInstall. Finally, put any 'unofficial' image on the card if possible.