The brief
The Golf had developed a metallic squeal under light braking around town, plus a fine vibration through the pedal on harder stops. A glance through the wheel showed plenty of lip on the front rotors. The owner correctly suspected it was time for fresh brakes.
Brake pads wear down a little every time you press the pedal, and the discs wear with them. When the pads get thin, a small metal tab built into them starts touching the disc, which is the squeal, and a disc that's worn unevenly no longer runs true, which is the vibration through the pedal on a hard stop. A set doing both of those has had its time, and you fix it before the pads run out completely.
The diagnosis
Wheels off, the front pads were down to the wear-indicator metal, which is as far as you let them go, and the rotors had clearly lost their flat sweep, with a lip worn around the edge.
Fitting new pads onto worn discs would just bed the fresh pads into the same uneven surface, so it doesn't make sense to do one without the other. It was a set job, pads and discs together.
The work
The front callipers came off, the worn rotors were swapped for new VAG-spec discs, and a fresh set of pads went in. The slider pins were cleaned and greased so the callipers float freely, and everything reassembled to torque.
Then the new brakes were 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 squeal was gone, the pedal was smooth, and the bite was back.
The outcome
No squeal, no pedal vibration, and full bite back at the front.
The Golf went home with the brake feel 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.