"At the moment I have to use a dealer to maintain my warranty"
DO you pay for your service? If you do you can have it done by anyone or even yourself. Some of the new models (if not all) have the service paid for in the new car purchase. These cars DO have to return for the service.
The law that regulates consumer warrantees is the Magnuson-Moss Act. Here is a pasted comment:
"Tie-In Sales" Provisions
Generally, tie-in sales provisions are not allowed. Such a provision would require a purchaser of the warranted product to buy an item or service from a particular company to use with the warranted product in order to be eligible to receive a remedy under the warranty. The following are examples of prohibited tie-in sales provisions.
The rest of the article is at: