Stupidly I put the blade on backwards, and on undoing the centre bolt to rectify.. I found that the shaft locking button for some reason won't stop rotation, and the bolt is less than halfway out and too tight to wriggle it out.
I have tried to carefully tap the top of the button when it appears to slightly hold the shaft, but still the lightest pressure on the bolt overrides the hold. There is obviously a fault there of some kind.
So I can't get the bolt out.. I removed the end cap of motor in the hope of perhaps removing the end bearing to enable a clamp on the end of the shaft, but sadly that doesn't look a likely option..also it seems there is no way to to get access to the shaft short of drilling and threading a hole through the casing somewhere near the button...
As an old retired motor mechanic this has got me scatching my head..Hmmm
So puzzle for the week chaps..Perhaps cut off, or drill off the bolt to get saw blade off etc?? or shall just shall I throw the whole thing in the bin?? Aggghhhh!

Keith, May 2017

Hi Guys,
Solved the problem!
I found, looking very carefully through the exterior ventilation slots, that I could put a thin screwdriver down between the metal fan blade, which jams the shaft quite nicely.. and I could then undo the end nut easily..Sorted.
Thanks for anyone who gave it some thought.
Best wishes
Keith

Keith B, May 2017