Hi JS
It's a tricky one about September isn't it! It all depends how confident you feel by then. If you are still feeling a bit insecure, then volunteering might boost your confidence and give you the push you need to get a job after Christmas. You can legitimately put on your CV that you wanted some time to make sure your dd was settled at school before taking paid work, but that in the meantime, you have gained experience by working with groups etc. supporting class teachers, broadening your knowledge of different year groups etc. by volunteering.
If on the other hand by September you feel more positive about teaching and feel that you are ready, you could try and get some supply work. There's no reason why you couldn't start with just one day a week and see how you get on.
I'm sure that a lot of schools still haven't sorted their PPA (planning, preparation and assessment) cover yet, so there should be schools looking for teachers to cover that - a good way to work in different year groups. I saw an advert recently for a school looking for PPA cover for 2 hours a week on a Monday afternoon - what a great way to test the water!
Like you, I really struggled when applying for jobs in the Spring, and in the end I applied for a private school where I knew there would not be any behavioural issues. My "bad" placement had been in a school with big discipline problems (actually, it was me who had big discipline problems, but the school was a challenging one nonetheless). Although it wouldn't be right for everyone, it was a lifesaver for me at the time. I only stayed there for 2 years, but it gave me the time to find out that in the right environment for me, I really could teach. I've gone on to work in 2 state schools which I much prefer, and now, even when faced with challenging situations, have no discipline problems because I'm confident in my own abilities and have had time to develop many different strategies.
Look at your Spring placement positively - it has shown you the sort of school that doesn't suit you. When you go for visits round other schools, you will know what sort of questions to ask and will undoubtedly have a gut feeling about whether you are in the right place.
Please CAT me if you need support over the summer.