After many hours of attempted self repair of an electrical problem with a VW polo I booked the car in with VW for electrical repair. Prior to collection of the car they told me on the phone that the repair was free of charge - the reason for that being that the mechanic only took 5 minutes which is too little for billing.
The standard cleaning of the car including engine cleaning came with it too.
Most appreciative to me was their honesty. Any other place would have charged at least for 1 hour of labor.