Mush,
I'll happily build you a pillar mate, as far as cost it wouldnt be a great deal, well in england anyway on mates rates, cant speak for spainish materials. My fee would be extremely low as it would be a nice thing to do, a bit out of the ordinary with the location!!. My view without seeing it 1st hand is, once the props are in place - Dig your hole and concrete, depth is dependant on ground?? then build the pillar to specification, a typical pillar in the uk would be 2.1mtr high and 325mm wide(brick &1/2) filled with blocks or concrete, the architect may want reinforcing st