Replaced the 2M frame linearity pot and that has reduced the random noise. Also replaced the boost line reservoir cap and the screen decouplers for sync sep. and frame output and its cathode bypass and the rather interesting cap coupling the HT to sync sep. cathode. I think I've replaced all the sync and frame circuit caps with the exception of the two 200pF mica caps in the feedback.
I think the linearity pot was the largest noise contributor although it still twitches a bit but Hugo's RCA integrator definitely helps.
https://youtu.be/t7Poh6CB0l8
Sitting back from the screen it's not perfect but much better than it was.
Peter