The easiest way to avoid any issues is to speak with the dealership and make it clear you do not want the vehicle washed, valeted or detailed prior to collection. This way you minimise the risk of having to correct their mistakes in future.
New vehicles will be covered in contamination due to the exposure of such materials during transport from the factory. Tree sap, tar and fallout bond to paintwork and can be tricky to remove. Pictured below is a brand new Ford Fiesta. The purple lines you see are as a result of a product dissolving ferrous metal particles. The chemical used helps to dislodge ferrous particles bonded to your paintwork.