Well, my copy from Amazon.de has arrived today, I got the same e-mail and entered the code,also the one for the DS9 uniform. It my account says the items are activated, but I don't get to choose the uniform ingame, nor is the Borg BO anywhere to be found.
1. Put in code on website.
2. Logged in to game and brought up the C-Store.
3. There's two tabs - one for claiming items and one for buying new things; go to the item claim tab.
4. Click to redeem Borg BO.
5. Open up your invetory, there will be an item with a Starfleet symbol icon. Right click this and use the item (might be equip, etc. can't really remember)
6. Now open up the BO assignments page and the Borg BO should be in the list
Edit: One of the devs said earlier that some of Euro bonus items don't come with the normal game code, but a seperate piece of paper somewhere inside the box, so to look between all the pages in case it got stuck somewhere. If it's definitely not there, open a support ticket.