The brief
The Polo had developed a vibration through the steering wheel and the brake pedal when braking, squealing and grinding noises, and the stopping had gone weaker than it should be. He brought it in. Those symptoms say the brakes are worn. A pulsing pedal means a disc that's worn unevenly and no longer running true, the squealing and grinding mean the pads are down to or past their wear indicator, and the weaker stopping is the friction material running out. Brakes are a wear item, and there's no nursing them past the indicator, so when they get to that point the pads and the discs go together, because fitting fresh pads onto a worn disc just beds them into the same uneven surface.
The diagnosis
Wheels off, the front pads were down to the wear indicator and the discs had a lip around the edge and measured past the minimum thickness on the gauge, with the uneven surface that was causing the pulse. Fitting new pads onto worn discs doesn't make sense, so it was a set job, front pads and discs together, to reset the braking properly.
The work
The front callipers came off, the worn discs were swapped for new genuine VW-spec rotors, and a fresh set of pads went in. The slider pins were cleaned and greased so the callipers float freely, everything reassembled to torque, and the brakes bedded in on a controlled road test, a series of measured stops to lay an even layer of pad material onto the new discs. The road test confirmed the pulse, the squeal and the grind were gone, the pedal was firm, and the bite was back.
The outcome
No pedal pulse, no squeal or grind, a firm pedal, and full, even bite back at the front. The Polo went home with the braking reset to like-new. Brakes are a wear item and there's no nursing them past the indicator, so doing the pads and discs together gave the car back proper, even stopping power.