Remove the brush housing (I am just using terminology as I see the parts, they will obviously have technical names that elude me so please be patient) this is described as "rocking it to and fro whilst pulling" I thought that the clear plastic would shatter if I gave it any more pulling and found that heating up the area with a hair drier very carefully worked with little effort involved.
Now short flexible pipe can be carefully pulled off.
Now remove the screw that holds the "cam plate actuator arm"?...its a black cup that is held in place with a short screw..remove it and slide out the shaft...the next two photo's.
Just for interest, I put an old cushion cover on the floor and stood the Dyson upside down on it so that I didn't damage the handle and it was at the right height for me to work on.
Next we can remove the screws that hold the "clutch cover" ? in place....next three pics, remove them they are all the same length.
Wiggle the cover off, it will give you some stick but it will come off...note that it has a long thin guide rod on the under part of its casing, mine was bent 90 degrees, straighten it otherwise you will forget to do it later, I could not see any locating hole for it but it must just support the casing.