Thanks Wheelrider but its not feeling too excellent right now. I have the all the bits fitted and cabled up now. For the additional gear cable, I cut some cable guides of a scrap ally mountain bike frame (cracked and not worth repairing) and glued then onto the Mezzo frame with epoxy. Here are some photos of the cabling.



First major test ride yesterday, the new rear mech is ok but a bit sticky on the way back up to the lower gears. This could be a cable issue but all new outer (lined) and inner cables were used. I have had to set the end stop on the mech so that it will not shift to the largest sprocket, it is 32 teeth and the mech is rated at 27 teeth. The cassette is the one that came with the hub, I will get a new one when the testing has been completed.
The next major problem is with the click box, it keeps going out of adjustment. I am not sure if this a sticky cable issue or if ther is a cable pull length issue between the Shimano selector and the dual drive hub. Some weeks ago I measured the full cable pull length from one end to the other on the shifter as 21 mm and the selector pin in the hub as 11mm. I assumed that the click box would correct this mismatch but it may not so I have some measuring and investigating to do.