I have just resolved what I thought was fret rattle which I could not find.
Eventually tracked the noise down to tremolo spring rattle which I had never heard of before.
By the look of YouTube it is not an uncommon occurrence.
I used this solution which I think was the simplest, and seems to have worked well.
The solution is a length of plastic tube 3mm ID. I cut it to the length of the stretched springs in the guitar
Click image for larger version. 

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