Thanks for all your feedback on this thread.

The brake shudder problem has now been fixed by my local repair shop - the fix was to replace the straddle cable and the lightweight alu hanger with a slightly heavier and far more solid steel hanger, the latter has made all the difference. Also the right-angled noodle was removed and the angle of the cable from the bars down into the cable housing is now gentler.

The attached pic shows the old cable setup at the bars but I'll post updated pics later today.