Please note that, although this is a fairly straightfoward job (well within the ability of most people), you do it at your own risk, and I accept no responsibility for loss, damage or injury, howsoever caused.
Start by removing the plastic engine cover, which is held in place with four plastic clips, similar to pop fasteners.
Simply pull each corner up gently, until the clips release.
To gain proper access to the intercooler pipe, you need to move (but not completely remove) the expansion tank, and disconnect the plug attached to the sensor, fitted in the metal intercooler pipe.
Begin by unclipping the green plug (indicated by the arrow on the right in the picture below).
To release it, gently lift up on the tag protruding from the bottom of the plug (the opposite end from the wires) and draw the plug off the sensor, then tuck it out of the way.
Next, remove the expansion tank, by pulling it upwards.
If it is stubborn, insert a narrow bladed screwdriver (eg. a mains tester - see picture 2) into the outside (ie. the side farthest from the tank) of the holding clip, indicated by the arrow.
then pull the tank upwards.
An identical clip is moulded into the rear of the expansion tank, directly behind the filler cap.
Once both clips are free, gently lift the expansion tank up and forward, toward the front of the car, and prop it up against the bonnet support.
The pipe to be replaced can be seen in picture 3, marked with two arrows.
To remove it, release the two jubilee clips (arrowed) and waggle the pipe free of the two unions.
Replacement and reassembly is a reversal of the removal process, but note the following.
Ensure the pipe is pushed up tight against the shoulder on the union of the turbocharger (the silver grey object directly behind the engine) and that both jubilee clips are properly, but not excessively, tightened.
Make sure the plug is reattached to the sensor on the metal pipe.
When replacing the expansion tank, secure it on the rear clip (the one nearest the filler cap) first.
Don't forget to replace the engine cover.
And that's all there is to it.