I've only ever had exemplary service from Porsche so either you were unlucky or you have a duff OPC (enough complaints about various ones on this forum)
£425 is the cost quoted under Porsche Fixed Priced Servicing, for those OPCs who participate, for a minor service. Major service is £495 (or £555 for an SD). Brake fluid change is a separate £95. http://www.porsche.com/uk/accessoriesandservice/porscheservice/serviceandorgininalparts/servicepricing/...