On average someone in the UK has a heart attack every two minutes. You have a maximum of eight minutes for help to arrive and for your heart and breathing to restart.
The Western Ambulance Service has a target of eight minutes although it’s frequently not possible to achieve. There is a First Responder but similarly it will depend on their availability and they may not be able to get to you any quicker. Having access to a Defibrillator increases the chance of survival by about 40%.