How quickly you can find the nearest defibrillator / AED can be a matter of life and death. When someone is in cardiac arrest and not breathing, every second counts. If a defibrillator is used within the first 4 minutes of a person suffering a cardiac arrest, their chances of survival can increase to 70%, compared to just 5% if defibrillation is delayed. It’s shocking really, but there’s no centralised, national database of defibrillators in the UK.
Check out http://www.nias.hscni.net/our-services/aed/aed-mapping/ that have lists of a number of AED locations.