stuttering fzs 600

[Fazerider]

...am now thinking.............REGULATOR/RECTIFIER............your thoughts please peoples

It's a possibility, a voltmeter across the battery terminals should indicate whether there's a problem there. I'm sure you'd have noticed low battery if the rectifier wasn't doing it's bit, if the regulator side had failed then the voltage could rise: maybe high enough to upset the CDI unit, but usually a high supply voltage just tends to kill things like that. And you might have noticed lights getting very much brighter as the revs got higher. So, have to say it's unlikely.
Did you try the suggested plug chop after holding it at max revs for a while? That should indicate if it's a mixture problem.
Otherwise, try a timing light... that might give some clues.