I've entered the code that came in the email from the retailer that I purchased the game from and I entered that code at http://preorder.eu.finalfantasyxiv.com/
The website gave out the normal errors that everyone seems to be getting but FFXIV ARR appears on the 'My Profile' page along with any other SE games I've purchased.
Now, do I require a second key from anywhere? Has the first key been accepted now? What about the normal SE account page? Does a code need to be entered there too?
Would anyone be able to offer some feedback please?