Hi, you will be able to go straight to Level 3. Is there still the option to do Level 4/HLTA course? In our area that would make you more employable as could take on more responsibilities.
I don't know anything about the specialist SEN course but would that pigeonhole you to working in SEN schools or as a 1:1 with very challenging pupils?
In terms of volunteering in schools, it is a tricky one. By volunteering in one school you will have more opportunity to build relationships, make yourself invaluable etc so that you are more likely to be considered when a paid role comes up. But by volunteering in two schools, you double your exposure.
Another idea - we have two volunteers on a TA course at the moment and they both asked to volunteer every morning. They are more useful to us in the mornings (when we do maths and English, less needed in the afternoons), can take on roles that require daily contact with specific children, are exposed to a range of classes and experiences.
IMO when you start looking for a job, the only thing that will matter is the quality of your volunteering experiences because everyone has the qualification. You want several year groups, 1:1 and small group work, exposure to a range of needs, experience of delivering interventions, supporting playground duty, everything, say yes to everything. Even inset days, ask if you can join any training being offered.