It is important to keep tabs on brake wear. If the brake quality degrades too much then when you really need to stop, you might not! Poor brakes will also be a fail on an MOT. In the following picture you can see that the brake pads are not making contact with the full face of the disc. This was due to brake pad wear but the effects of this caused the disc face to become badly uneven. In this case, both the discs and pads were replaced.

To change the discs and pads, park with the handbrake on.

Locate the jack under a safe point of the car. Either use the jacking point or if your car is too low, locate the jack under the front wishbone!

Slacken off the wheel nuts, and then proceed to jack up the car, and remove the wheel.

Using a 13mm Socket, and a 17mm spanner to stop the slider moving, remove the top calliper bolt.

Swing the calliper cradle down, and if possible support using a stand (or similar) to avoid putting excessive strain on the brake hose.

The pads will just lift out, if you are only changing the pads, simply refit the cradle.
With the pads removed, you now remove the calliper, using an E18 socket (or a 14mm socket fits well), locate the 2 calliper bolts with a bit of blind faith!
These are located on the reverse of the hub-mount.

This will hang by the brake hose, I would suggest that it is just supported on a spare axle stand. Whilst the calliper is off, squeeze back the piston into the cradle to create more space.

Undo the Brake disc retaining screw using a T30 torx bit. Remove the disc.

Some brake discs have a protective film that needs to be removed by cleaning them with brake cleaner before fitting.

Line up the new disc, and tighten the T30 retaining screw.

Refit the calliper on the hub using the E18 socket.
Fit the new brake pads, use either copper grease or anti-squeal shims on the contact areas on the back of the pad.

Swing up the calliper, refit the bolt using the 17mm spanner and the 13mm socket.
Refit the wheel, and do the other side!.

*** Pump brake pedal with ignition on before driving ***