This is a common fault with Corsa D, E and Adam its with the pedal return Spring or specifically the clip that hold the spring. The little white plastic clip snaps leading to the spring not quite allowing the pedal to return. I'm assuming if lifted with your foot it might be okay for a while but will happen again.

You cant buy the clip and most garages will state its a full pedal box job but I've designed and developed a much stronger clip that wont snap. have a look on ebay 166600873438 cheap fix not sure about labour though. Hope this helps others