Thanks to all, Have found a Zeobrite dealer, 35€+20 delivery for a 25llb bag. Seems to be the best stuff if it does what it says, got til next year to decide! Will get some squidgy soap stuff when I'm back in blighty next. Got some good friendly advice from Jardi y Piscinas in El Perello near main square up a side street. v. reasonable floor vacuums at 22€.
Paul