Hi Chris. Here are a couple of websites with guides on how to remove the clutch:
This one has LOTS of photos!
http://www.dysonmedic.com/DC07%20Folder ... ement.html...and a video guide:
http://www.espares.co.uk/advice/vacuum- ... 4-dc0.htmlThe clutch is accessed from inside the cleanerhead rather than via the coloured knob. It looks like you need to remove the cleanerhead from the body to gain better access before you can remove the knob. I've done it before but it was a long time ago.
If the guides look a bit overwhelming don't worry. If you've stripped down a Dyson before you shouldn't find it too hard.