Got the tank and air filter housing off at last, to get access to the 2 connector blocks, the 3-way connector from the alternator and the 4-way from the regulator. The Haynes tests for the stator were spot on - each wire had 0.2 - 0.3 ohm resistance and each had no shorting to earth.
The tests on the r/r were less clear. On diode setting on a cheap multimeter, it was giving readings of 542 where Haynes says 0.4 - 0.7, and of 1082 where Haynes says 0.5 - 1.2. Which I'm assuming is all good. But on those combinations where Haynes says 1.4+, it gave no reading at all. Having limited understanding of electronics, I'm not sure if that is a good reading or not - presumably showing open circuit?
Thanks for the flow chart Gassoon, though some of it would be difficult as the tank and air filter have to be off to get at the connector pins, so you cannt start the engine to do the tests. There isn't enough cable to pull the connectors below the frame to enable access to them with the air filter housing and tank back on. It is a crazy design.
After pulling various connectors apart all of which looked good and re-connecting them, and looking for frayed or burnt wiring, I put the air filter housing back - a dementing job, then the tank and started her up - but just the same absolutely no charge going to the battery.
I guess the next job will be to take off the stator and inspect it. Is the stator/magnets running in oil or dry - do you have to drain the engine oil before removing the alternator casing?
Or is there anything else to try first?