There are different grades of Brembo discs and a lot of fakes. Buying from a dealer should ensure you get a decent Brembo part rather than a value line part, or a fake.
However other companies can and do make decent discs and pads without the "Brembo" tax. Personally I really rate Delphi.
If you want excellent performance and value, not necessarily Brembo, and don't need the floating discs, I suggest these:
Front discs Delphi BG9327C identical to the MB part but perfectly made and packaged (MB discs can be bit battered)
Rear discs Delphi BG9211C again really nicely made and packaged
Front brake pads Delphi LP2149 - Low metallic, in theory lower dust, still excellent performance
Front brake pad sensor Brembo A 00 470 (similar price to anything else)
Rear brake pads Delphi LP3516 - Low metallic
Rear brake pad sensor Brembo A 00 470 (same as front)
Rear handbrake shoes - usually pretty crusty and worth changing - MB A0044208620 - Mercedes because you get the full fitting kit, including the arms, and they're only about £40. Note that these are made by and labelled Jurid (as well as Mercedes).