We used to use P3 too and it was great! How often do you get free airport parking?
But, those days are gone now and there is no free parking at all.
Last time we used a service run by "Chips Away", I think that's what they were called, who take your car from the airport and bring it back when you return. I think they carged €5 per day.
There are several companies doing this.
Read more about Malaga airport parking here.
Justin