Interesting point,In the car trade,there was something called 'Block-Exemption' introduced,which basically allows car owners to choose which Garage THEY want to service/work on their cars,irrelivant of brand,and as long as the cars are serviced to 'original manufacturers' standards,they keep the warranties valid. Unsure if this includes doing your own servicing.Will find out tomorrow at work and let you know. (I work at a car dealers,SEAT unfortunately)
Speedy
