Hi,
Sorry no feedback for a while but work gets in the way!
Warning light still no working but not had time to work on it - I have fitted a voltmeter which show 11 volts on start then goes up to 14 volts after a minute or two (or after a bit of revs) so I am still thinking it may be the diode and I will follow Pauls advice next weekend and see where it leads. On the plus side it cruised through the MOT.
Will let you know how it goes.
Cheers guys,
Kev