For the record it might be that the 2 versions are actually identical. There're diffrent Technical support and EULAs, and different files in the text_assets folder (binary). They probably didn't changes subs while keeping voice the same. But maybe they changed UI and text on in-game textures?
Topic on Talk:Dead Space
Why would they though... it's an American game with American actors, and so on... British people have no problem understanding American/Modern English. So why go through the trouble, time, and extra-work to add some redundant letters to words? Goes for any game btw.