Had this annoying little noise begin and sure enough it was coming from the rocker area, it isn't as light as a big clearance tappet 'tap' but a slightly deeper chatter.

I did notice upon reassembly some weeks ago that one or two of the arms had a hesitation but I didn't think it would have affected things as it was only slight.

Could the hesitation have worsened and started making this chattering noise due to all the friction?

Noise is not audible at idle rpm but it is most audible up the rev and down the rev (carbs get too loud to hear anything between the rev up and rev down).