Update on the Science Programming in my Town - What are the next legal steps?

So I posted in my town's group page and a lot of people are highly interested so much so that I have a school wanting to hire me to come in once a week to teach a science portion during their lunch period as well as HomeEd groups wanting to book weekly lessons. There was a bit of backlash on the prices of the classes. People wanted to only pay £15 which is fine and completely understandable, but the more in-depth classes cost me more to supply so some classes are going to have to be at the £20 mark which some people aren't happy to pay the extra £5 but I can't put myself in a financial bind, especially when I'm on the spouse visa.

Now, here comes the stuff that I need help with because I have no idea where to start. I know that I need to get insurance and register as a self-employed person. I have a National Insurance Number for all the tax-related stuff. I'm going to list out the questions that I have because I haven't been able to find a direct answer.

• What kind of insurance will I need? As of right now, I won't have anyone else working with me to teach these Science workshops.
• I'm planning on still working while I try to start this up, I'm hoping to make it a full-time thing in the future but for now, it's just not financially possible. When I go to do tax stuff, how do I fill out the paperwork? As I'll be partly self-employed and also working part-time somewhere else.
• Should I create something for parents, schools, and groups to sign before I come to do the workshops just to cover myself in case of any (highly unlikely) incidents?
• A few parents have stated that they don't want to attend the workshop with their kids, which is fine, but what would I have to do in that instance? I have a recent DBS and also an FBI background check, but would I need to register with Ofsted (whatever that is)? The workshops are only going to be between 1-1.5 hours long.