That is the correct part and I have assembled the gearbox.

Whilst spinning the cam plate through the gears I noticed one or two issues.

1. There is a track worn into the cam plate by the cam plate follower and

2. At some points - namely 2nd and 3rd gear there is a pronounced dimple worn into the surface by the follower and where the follower naturally rests when in that gear. The lip of the dimple is quite steep and would appear to catch the follower when moving out of that gear.

So - does this mean I have to get a new cam plate (approx. £75 or so) or can this be smoothed or ground out. I'll try and get photo's when I disassemble later this week.