You can find the most recent list of first aiders here.
If you need a first aider urgently during working hours, pick up an internal phone and call 222; the operators will find the nearest one for you and send them to your location (out of normal working hours the 222 call will divert to the Emergency Services).
First Aid at Work certified persons will have attended a three-day, HSE approved training course with a two day refresher every three years. These people are the first point of call in an emergency situation and are required to respond, irrespective of their current activity (unless leaving the activity would be unacceptably dangerous).
Emergency First Aid at Work certified persons will have attended a one-day, HSE approved training course with a refresher every three years. These people are available to provide support to First Aid at Work first aiders and are trained in basic emergency first aid.