So I ordered the bearings from Simplybearings,
1x NSK 6805Z (this was knackered)
1x NSK 6808D
The bearing puller I ordered, Amazon 4 inch small bearing puller.
You need a torx (star shaped) bit to undo the cover on the case.
To split the case I tapped all the way around with a plastic hammer, put the bolts half way in and tapped on them all the way around, and then using a blunt (round edged) screwdriver to gently part it, without marking the mating faces.
Inside the top cover are two sprung shims, take note of where these go, take out and clean.
Then lift the through axle out, with dead NSK 6805Z bearing attached.
Twist and pull on the two gears (black plastic one and one beside), this will unseat the bearings in the bottom case and they will both lift away. Notice there is a sprung shim under the metal gear side, but not under the black plastic gear.
Then undo the four screws which hold the speed sensor and plastic housing, once this is done you can fold them back out of the way. I was careful not to touch any of the circuitry on the boards, because I know how easy things can get fried.
Then you will see the main drive or final drive that adds assistance when you pedal, this whole unit can be lifted out in one, and consists of speed sender on one end, a one way clutch connecting the final final drive gear, and one NSK 6808D bearing (this bearing was ok on mine). Inside there are 3x needle bearing cartridges, you can remove and clean these and regrease, (one requires a seal to be removed and refitted).
Using small bearing puller, I removed the 6805Z bearing from the axle (a 2penny piece works as a blanking plate on the end of the axle for puller to pull against),
Then after cleaning axle and greasing, using a flat ended punch and a hammer, I gently tapped the inner race of the bearing, little by little turning a quarter turn each tap, until the bearing was seated against the stop.
Do this carefully so as not to damage bearing or axle!
After this is done and all other bearing checked for smoothness, it's simply a matter of patience, I cleaned out all old grease from the case, gears, bearing seats, sprung shims, the one way clutch on the final drive gear, then once everything was clean, regrease everything and reassemble.
I used a strong solvent to clean the mating surfaces of the case, and then used a tiny smear of Blue Hylomar to seal the case.
.........and that's it!
