Jaguar poor service

My wifes car broke down, it is the electronics in the centre console that needs to be replaced. Jaguar do not have the part and says eta on it is 2 and a half to 3 months. They are not willing to give her a courtesy car as her car is not under maintenance plan, but it is there falt the car is standing in there workshop, because they do not have the part. My wife uses the car for work and is her only mode of transportation and to pick up our daughter at school. I feel this is not the kind of service you would expect to get from a big brand like Jaguar why do we then spend exorbitant amounts on services and repares through there dealership if this is the service you recieve when they can not deliver the part.