I have to disagree with you there Roff.
On my car (a Ford Mondeo), when the cruise control is set, the accelerator (throttle in US parlance) just sits at its resting position.
If the driver touches the accelerator the car will speed-up and when the driver takes foot off the accelerator again the car will slow down to the cruise control speed.
If the driver touches the brake, the cruise control is cancelled until the "resume" button is pressed.
This behaviour was the same on other Ford vehicles I have driven recently, a Focus and a Galaxy.
JimB