Hi I have replaced my rear brake pads in my 320i. My rears are a little different than in bigger 3ers. I have a single rotor non ventilated and a caliper as you can see in here
So I bought the textar pads 50euros plus a sensor 15euros. In pads set is everything you need the pads ,the sliders (number 8) and two bolts (the number 3 in the diagram).
So I removed the downside 3 bolt and rotated the caliper without moving the base and free the pads.
The most difficult part was to place the sensor on the pad. I was trying for an hour but the f@ckin thing did not want to seat properly. It needs the right angle and not too much force. Finally it fitted properly after much cursing
Hope I help someone with my experience.