We also had somebody knocking on our door, I smelt a rat and sent him packing when he made some random names up and said they had donated 20 euros. Since we were the only people living on phase 2 at the time I wondered where he had got the names from lol.
Since then I have heard it is illegal to collect door to door in Spain,I'm not sure how true this is though, so if anyone can clarify it!