I've looked into this myself and as far as I'm aware you have to do the Diploma in a Social Work. I think before you could be a trainee, but not anymore. I'm afraid that qualifications is necessary.
If you have any connections with the Social Work Dept, eg as a Foster Carer, you could ask if they need any help to supervise access visits or take "customers" on trips etcetera during any free time you may have. Once you've been checked out and built up a reputation you could find yourself being used more and more. It wouldn't be easy but if you could do a bit of studying as well it could be a way of getting a foot in the door.