How can I remove the wheels from a Dyson DC 08 vacuum head?

After a few years of use there is very limited movement in the wheels of the vacuum head, there is a blockage of fluff, hair etc that has accumulated around the axle. Much has remained despite digging in with a sharp knife etc, the only way to get rid if the rest seems to involve removing the wheels...but I just cannot get them to pop off. All help accepted