Adam
I had to remove my main wheel recently (to repair a puncture). As far as I can recall there was a brass washer with a second smaller nested brass spacer on the starboard side, and there is supposed to be an outer angled 'tab washer' on each side which functions to hold the undercarriage doors clear from the tyre when the gear is retracted. (In my case the outer tab washer was missing on the port side, so I need to either source one, or get one made).
Martin