Back to the original post, I would say they have done everything they needed to do for you, ie sort out the bumper. The problems lies in the way they dealt with you on a personal level, ie telling you they would do it whilst your wait when that was far from the truth and lack of communication. Use the feedback from that the dealer gave you and be honest on it and if that means criticising the salesman,then so be it, that's what it's for.
You won't get anything for it, you have no right to compensation from what I've read, just give them the feedback and leave it at that.