What should I say?

[Shiny]

You can really say what you like, so long as when it comes to doing your tax return and you're claiming expenses etc it ties in well with the title you've given yourself.

I don't think the expenses have to tie in with the description Ana_X.

In very simple terms HMRC are only concerned about you paying the correct amount of tax. Provided you are declaring all your income and claiming all (tax) allowable expenses HMRC won't be bothered how you describe your business. The question will not arise anyway until you're selected for a tax inquiry, which may never happen.

Then, and only then, would you have to tell HMRC that your business description doesn't "fully describe" what you do. HMRC have to treat this as confidential anyway. Tell them what you do and they will allow all the (tax allowable) expenses you've claimed.

Yes, even if you call yourself a French Teacher you can still claim the cost of condoms, work related clothing, accessories, etc.

I have self registered this morning online. And went for 'performance artist'. Thanks for your help.