So, done - took about 3 hours over two evenings as I needed to drill the mounting for the Regulator. First though I had to borrow a Drill !
Anyhow, I can report that the Enduralast kit is well documented, well put together and of a high quality. Instructions are also excellent and everything needed is in the box, including even a Rotor drift, which surprised me.
Lots of crimped connections - which I'm not 100% happy with, may have to heat solder to get peace of mind. But I got the new 450w Alternator, Regulator on and wired and the bike is charging again.
Seems like it's very powerful and is well engineered - all the old stuff has to be stripped off and dumped.
Even at low revs it pumps out 14.3 volts so looks good.