I’ve always had Courtesy cars for service’s They just say the 1st dates that one’s available on. honda asked if i needed an auto but vw and other’s have not or just don’t have them.
For other issues or for the mot then i go there and wait, any work doing they need mb’s authority and then often have to order the parts and then do the repair at a later date.
unless it’s a wiper that needs doing or an the oil levels suddenly low. So really it depend how long it will take..