I'd go elsewhere to be honest if I were you - but I'd make a point of it with an audience I kicked off big style in Leeds VW once and then other customers who heard me joined in agreeing at how 'sheet' they are.. was very amusing.
Sounds really mature that
I've always been more than happy with the service Huddersfield VW has given me. The policy of not giving under 21 year olds courtesy cars obviously exists for a reason, and yes I can imagine it could be inconvenient.
Regarding the point about a courtesy car being a 'privilege', well that's exactly what it is. Look the word courtesy up in a dictionary. Why exactly should a dealership supply a courtesy car to every Tom, Dick and Harry who is having a little bit of work done on their car?