Just found out how to do this out before I destroyed the cover too much.
Make sure you've disconnected the mains plug first.
Then you need to remove the handle, this is the 1 screw at the back, then it pulls off towards the back (you can also push on the screw). Then remove the 2 screws below cover - just inside the bag dust cover.
This may be a bit late for Dave, but hopefully will help someone else. Ta
Mark, August 2008