Diesel or 1.2 or Twinair?
Did it just happen suddenly?
Any work done recently? Could have disturbed connectors etc.
Car's history (bought it like that/owned for years etc.)? Usually some signs of impending failure before total loss of pedal control due to wear.
Any other recent problems (flat battery, etc.) Could point to failed earth lead, et
Any likely cause (just drove through 3 feet of water, etc.)