Avenger
Not so re NAS contract pilots all are employed by agencies and the contract prohibits "self employed" status.
They get holiday,sick & standby pay and are taxed at source by the agency in accordance with their base. They also receive an additional block hour payment based on what you did, not what you were rostered to do, so yes holding and diversions are paid. The ratio of contract pilots is around 25/75% compared to permeant employee's (B738 Fleet)
Non of the agencies are Spanish