Selling Luxury 2 Bed Apartment Los Granados De Cabopino

Hi all, My folks are looking to offload their luxury 2 bed ground floor beachside apartment in the beautiful Los Granados de Cabopino.  They have already bought another property and are anxious to sell this one on pretty quickly.  What are the best websites to use to advertise this privately, either in Spain or in the UK.   Are there any other avenues to pursue when looking for a quick sale of such as high value property.

Thanks

MARY