Yeah you can override ACC anyway with throttle input - eg its set to 70mph but suddenly for "safety reasons" you need to achieve slightly more, just boot it.
When you come off of the throttle it slows back down to whatever it was set to before.
You can ever override the speed limiter (if you ever use it) by kicking down beyond that notchy bit at the bottom of the throttle pedal travel. Through that gate and it ignores the speed limit set.