You'd be surprised how little you need, so don't be intimidated by that.
My degree was a 2:2 in philosophy and theology (I can't think of anything more useless for a job) and I got onto a computer science course. Nobody on my course had any programming experience but that's kind of the point of a career conversion.
My choice wasn't for everyone, but with teaching experience you could be a strong candidate for something like social work (my wife does adult social work, helping the elderly with their care needs, so doesn't have to deal with the difficult children's cases you hear about in the news). Also there's very little required to do business, accountancy etc. It just depends what you're interested in.
I chose this route because I knew in the field I wanted to go into that it would be important to be able to tick the bit of the person spec on jobs which said related degree. Not all jobs are like that but it can be difficult to get one with decent pay without some sort of qualification.
One consideration is that this sort of choice can be expensive, you may need to take a pay cut or go part time for a year to get a qualification as well as being able to pay for it. You may also be starting at the bottom of the ladder again when you restart.
I personally can't recommend leaving teaching enough, I think it's insane what teachers have to do even in nice schools to work in. However, you may only get one shot at starting a new career, mainly because of the costs, so think carefully about what's a good fit for you.