Hola Simona,
Like someone else says in another reply, the Gaudi buildings are a difficult part in the negotiations, and there are many other buildings to be seen.
The best is to establish a collaboration between us (you and a local producer) and the Catalunya Film Commission. The film commission will collaborate to open doors, but it is us, service production companies and location managers, who have to actually do all the scouting, negotiations, paperwork and services coordination in the end. I am used to deal with the film commission and they are usually very helpful on the side of putting us in contact with the right people at each place to negotiate.
I am available to speak whenever you are ready.
We can skype if you prefer.
Email me at info@bonitasproductions.com and let me know.
Good luck with your project, wether we end up collaborating or not.
Eva Piqué.
Michael Claughton 
