Originally Posted by ameba
...Would the arrival from EZE also count as an international arrival not allowing me to do LHR-BCN since I am entering the country of origin twice?...
IMO, yes, once you get back to Spain, that's it, no more international departures.
Edited to add: No D availability EZE-LHR, on such a future date seems odd. May I ask what dates you are trying to book?