I just managed to work it out!
The white cover hinged can be removed - push in the lugs where it hinges, and then you can wiggle the whole cover off.
The front blue moulding has 2 screws near handle and has lugs that hold it under the back piece but you can prise these lugs out with a screwdriver, thus you can remove this piece. This then reveals 2 screws for back blue moulding (as well as the 2 under the rear filter exhaust filter cover).
Once again the back of this blue piece has lugs that clip it into the grey bit at the back, but will prise off with a screw driver. This piece will then come off.
Bob's your uncle! the cable winder and motor assembly is now revealed.