Thank you, Jack, for advising me of that particular thread.
All apart now and only the cleanup and reassembling in front.
As a note for anyone else who may attack one of these, I used a couple of tapered cold chisels (don't faint here) to drive between the pulley and the chassis - not to cut anything, but they just happened to fit well in the space and the taper allowed for a gradual interference.
Once the pulley was off and the keeper/grub screw removed, it virtually fell apart.
So, I would suggest that the trick is to undo the bearing keeper from the outer side, then the grub screw (which was an Allen head screw on mine) and then pull the pulley off which takes the metal inner gear with it (as can be seen from the pics).
The plastic drive gear comes off when the centre shaft is driven back into the roller by the method described by Kempe (nut back on the shaft and allow the weight of the rollers to force the gear toward the ground) I then used a long podger that I had from blacksmithing days to drive it all the way through.
Pictures follow & thanks again for your interest.
John
