They only give out the UC if you can prove you've bought the game sometime in the past. Your best option would be to see if you can buy the basegame somewhere so that you can present customer service a registration code. That way you'd get everything for the price of just one basegame. Not free, but still very much worth it!
Edit: Not always true, seems whether or not a code is needed depends heavily on who is manning customer service at the time of calling