These breather pipes comprise two rubber joiner pipes, a solid pre-formed section, and a one way valve from the crankcase to the throttle body.
It is not uncommon for the rubber pipes to perish, spraying oil everywhere, or for the valve to fail.
The valve either sticks closed so the crank case pressure cannot escape, or sticks open, so when you are under boost, this pressure is also being forced back into the crankcase.

The part number is Q0003134V008000 ("Breather pipe part thrott"), and will cost just under £15 from smart.

Remove the car's rear panel just to give more space (but this can be done without removing it); the guide is here.

If you have aircon, you can see how little room there is to reach the breather at the entry to the crankcase. So you will need to lower the engine to give you more space. If you do not have aircon, there will no compressor and you can easily reach to the other end of the breather.

Chock the front wheels.

Look under the car just in front of the rear wheel for the sub-frame mounting bolts.

Use an E18 socket to slacken this off, wind the bolt until approximately ½ to 1" of thread is showing.

Now slowly jack up the car until the rear wheel lifts off the ground.

Now slacken the corresponding engine subframe bolt on the rear, and slowly lower until you have room to get your hands in.
You may need to just slacken off slightly the 2 nearside subframe bolts too. This will allow the frame to have a twist on it, as only one side is jacked up.
You will only gain about ½ - 1" of extra room, so the space is still going to be quite tight.

Remove the vacuum pipe from the fuel pressure regulator.
Remove the connection to the throttle body.

If you have air-conditioning, you have even less space to manoeuvre, but the breather pipe connects to the crankcase just to the offside of the a/c pipes.

Reach around the back of the pipes to ease the rubber joining pipe from the crankcase. You can get someone to pull on the remaining pipe section if it helps.

Take your new pipe.

Reach around the back as before to push on the new pipe; it will go onto the connection much easier than it came off.

Ensure the routing and angle of the pipes are okay, so there are no twisting forces on the rubber joiners which may cause premature failure.

Reconnect the pipe onto the throttle body.

Reattach the vacuum pipe to the fuel pressure regulator.

Raise the engine back up to the subframe and re-tighten the bolts.

Lower the jack, remove the chocks, and just do a final check that the subframe bolts are tight.