I purchased a 65-plate Skoda Octavia vRS 230 from Skoda Watford in November last year and while I love the car there's been a grinding sound when driving and braking since purchase. I had the car in for a service at Skoda Croydon on Thursday last week and asked them to investigate the sound, which they say is being caused by rust on the edges of the front brake discs. I'd need front pads and discs to rectify at a cost of £275. Would it be reasonable to expect Skoda Watford to repair this as a pre-existing fault? If not, would having the work done at an independent garage to save a bit of money but void my warranty?