Hmmm, should of looked closer - just above the foot rest, there is a plate - take this off and this exposes the two bolts that hold on the heat sink. Of coarse the bolts holding the rectifier to the heat sink had to be drilled out - but at least it's replaced.
Did not see the plate at first, as one of the bolts holding it on looks like a main engine bolt or something.
Hope this might help someone else.
And also, the bike now won't start - but that's a problem for tomorrow