This is why I mentioned earlier. It depends specifically what part of the brake system we are talking about here. Pads and discs are consumables. If they have gone withing a day of leaving the forecourt, more than likely you'll just have to lump it or perhaps get a good will gesture from the dealer.
In this case though, a brake master cylinder should be covered under whatever warranty the issuing dealer has supplied, and definately covered under SoGA.