As per the previous posts, vibrations from the brake could be caused by a number of things.
I thought most decent garages ensured that they applied some copper grease to the brake pads when these get changed to ensure there's no kind of squeaking.
If you feel a judder through the braking pedal at any speeds, this is usually a sign of warped discs.
Pads are comparatively cheaper than discs but hard to say what is the cause in your case.
Another thing to keep in mind is that if the discs are warped, make sure that the wheel hub is fine too because if this isn't in good condition, this will also cause issues with braking too