I have delved further into the snag and have repaired the turn signal problem, which turned out to be the wire in the switch having somehow released itself from the screw-down terminal. A somewhat fiddly job getting the wire back into place and tightening the retaining screw. The buzzing continued and intensifies with firmer brake pedal application. I am going to borrow a DB10 that I know is serviceable and see if that is the cure. I have plenty of time now, as the car has been prepared for its winter sleep after we received a good measure of snow a few days ago. I will update you with the results of the DB10 swap when I have completed it. Just as an aside, the serviceable DB10 will be being provided by an MG TD owned one of my pals. The TD has the same brake/signal switching function as the Mog.
