Sounds like the drive belt to the clutch mech is stretched and slipping on the drive shaft. The clutch assembly cover is accessed with 3 torx screws. It is tricky to remove as it has a 'pin' guide through to the bottom section as well as being behind the brush roller plate. But it can be persuaded to come out. But if you need to fit a new belt - that's a whole new ball game....
Malcolm X, September 2007