You can get pads and discs from most motorfactors. However if you want something decent then your obviously looking further afield. EBC and GreenStuff spring to mind as quality brade pad and disc suppliers.
I hate motorfactor parts, my local one does motorquip products, their pads would stop the car quicker if they were made from wood, though maybe they are!
Ive used A-Pec brake pads before, these are quite good. Though i think they are one of the cheaper brands they are up to the job, On my car they gave good feel and performed well at all times. Though if pressing on on some good roads it was possible to get them to fade all to easily. But under normal use they were fine. Wheels soon turned black though.
Greenstuff are said to be good for giving off less brake dust than normal.
Discs seem very similar really, i cant tell the difference between geniune dealer discs or cheap ones. IMO its the pads which made the difference to braking performance.
I told im very heavy on the brakes, and i do like them to feel right, i tend to go for as good quality as possible now. Though i never buy them from the dealers, usually a rip off price for brake parts.
You could always use
http://www.aepdirect.com/ if you want something half decent and with good service.
Chris.