If you are not going to go main dealer then I would look at brands like Textar or ATE, these companies manufacture brake pads & discs for BMW. I have noticed that most BMW pads are actually Textar, discs are ATE & handbrake shoes are Jurid in BMW boxes. The likes of Otto, Super4, etc. should be able to supply these OE parts.

OEM pads seem to produce a good bit of brake dust but work reasonably well in the real world.
I don't think I would be fitting €20 brake pads to the car.