I make no guarantees of this, but I´ve just bought RENFE tickets over the internet for the first time (their system doesn´t accept UK postcodes either, incidentally). I took the option to print the tickets at home and that was it - no need to queue to pick anything up, at the barrier we just showed the paper tickets I had printed and got on the train. It´s not what they tell you to do on their website, for all I know it might be a glitch in the programming for the booking system, but it worked for us.