Just found this thread and it has given me a great deal of merriment. As a former Flight Engineer and full time cruise autothrottle on the Tristar, when the speed went up unexpectedly, I would pull the no2 throttle lever back an inch and wait. It was busy work on the way to Japan some days but I never had a high speed or low speed warning. All smooth with no checklists, speed brakes, recall items or need for the PF to pitch up. Looks like the modern ones are hard to handle despite the automation.

I've been away from this forum for quite a while and for my surprise I found out this thread is still "alive".

Like I said in a post before, the most sensible approach for an overspeed recovery on the A320 is... doing nothing! Simply sit and wait and monitor if the ATHR is doing its job. Don't touch the AP and most particularly don't use the freaking SB at very high levels.

KISS.