Hey there! I'm currently a PTA (Patient Transport Attendant) with SJA; i'm going to try and answer as many of your questions the best I can
1. The best way of joining is to visit your local group and speaking to the leader. This way, you become familiar with the team and other volunteers and they can assist you through the joining process. And within reason, everybody I have known has gotten in. If you have medical issues etc your level of volunteering will be tailored to these.
2. The training process has changed recently. Before you become a first aider to must qualify as a TFA, training first aider. I never went through this process so I can't help you out too much! (Hopefully a newer volunteer can chip in here..) However, the courses usually take 2/3 days.
3. Your level of commitment is entirely your choice. There as requirements, they are however very low. I think it's 50 hours a year. 30 hours from training/weekly meetings and 20 hours from duties. It's very easy to exceed this. I did approx. 180hrs last year and that was along with studying for my A Levels. Speaking for my division; no pressure is placed upon you. Are you a volunteer!
4. Your daily tasks will depend entirely upon the duty you have attended! You may be putting plasters on children's knee's for the day! Or dealing with a major head wound, or you may find yourself in a resuscitation scenario. When people come to you for first aid they do not know your level of training; you must do what you can and call for back up should you require it
5. Definitely relevant for a nursing application! Around 75% of our volunteers are nurses/paramedics/students studying such subjects!
An experience from me? Two big ones I will always remember! My first MotoX event a lad flew from his bike, fractured his femur in three places and his spine; airlifted to hospital. Such a good casualty! And the second was my first resus. Sad situation since I had cared for the lady for two years, however, knowing what to do and knowing that I did my very best for her is always a comfort. There's a huge support network within SJA to help you cope with scenario's that affect you in any way.
Hope i've helped somewhat! Let me know if you'd like to know anything else