Try looking through business link or click
government startups website
I was self employed as an instructor for some schools and employed for others so have done both. Would also suggest a quick look
here .
Of particular importance is to have a look at what IR35 is and means to you and take professional advice before deciding whether to form a limited company and employ yourself under schedule E or be self employed under schedule D tax regs.
The issues are not complex but you must put yourself in a positon of strength when dealing with tax as the government are fairly inflexible when it comes to money that you should have paid and ignorance is no excuse also the clubs/schools that you teach for are probably forcing you to go self employed as it is in thier interests rather than yours. This is due to issues such as employees insurance liability, etc I solved most of my problems by marrying an accountant but PM me if any issues come up that I can help briefly with.
Bonne chance