Took photos while doing it and couldn't actually find a guide on here, so here goes!

You will need:
[list]
[*]Stanley knife[/*:m]
[*]10mm spanner or socket[/*:m]
[*]circlip pliers or needle-nose pliers[/*:m][/list:u]

First, open the boot (duh). If that needs explaining, stop now and find someone else to do this work for you

You need to remove the trim piece around the boot catch on the back of the car. To do this, there are two nasty trim clips holding it on. Use a stanley knife to pry the centre of the clip upwards, and then remove the whole clip with your fingers. The clips are located here:

[url=http://s764.photobucket.com/user/hughiew/media/IMG_20140430_141226_zps2kqrzzpx.jpg.html][img]http://i764.photobucket.com/albums/xx287/hughiew/IMG_20140430_141226_zps2kqrzzpx.jpg[/img][/url]

Next, you need to remove the side pieces - these have about 12 million of those clips, so get cracking! You only need to remove the right hand side if you're only after the aerial. First clip is right in front of you, where you just removed the first bit of trim. There's another up near the rubber boot seal, another sort of in the middle of the big trim piece, and another down near the seat bolster (lower the rear seat). This one is a pain to remove (I actually didn't bother, just let it fly off into the universe when I pulled the trim piece out )

Now, pull out the trim piece - it should rotate around the far bottom corner which is hidden behind the back seat bolster, and pull it around the rear seat hook. Wriggle it until it comes either completely off or at least out of the way.

The aerial itself is held in with one 10mm nut, and the retaining ring on top. First, unplug the aerial and power connectors (easy enough), and then take your pliers and stick them in the opposing holes on the top retaining ring:

[url=http://s764.photobucket.com/user/hughiew/media/IMG_20140430_141601_zpswewysdqq.jpg.html][img]http://i764.photobucket.com/albums/xx287/hughiew/IMG_20140430_141601_zpswewysdqq.jpg[/img][/url]

Rotate anticlockwise until loose, then you can use your hands to remove it fully. Once that's done, undo the 10mm nut holding the aerial in place.

[url=http://s764.photobucket.com/user/hughiew/media/IMG_20140430_141556_zpszrkhtial.jpg.html][img]http://i764.photobucket.com/albums/xx287/hughiew/IMG_20140430_141556_zpszrkhtial.jpg[/img][/url]

You should now be able to wriggle the aerial out, and then disconnect the drain hose at the bottom (these are properly stuck on, just keep pulling!)

Job done!