Sole trader needs some info?

[Chocolate Guy]

It doesn't matter how much or little you earn, it's a fact of life you need to pay tax. There are many who would say take the chance, but if you do and get caught the fines are huge, not to mention it will completely destroy your young business.
With modern technology it's only a matter of time before HMRC discovers you selling anyway.
It also depends on what you are selling as to whether you need to register with other departments, food hygiene etc.
If you want to keep your business name, then at some point it will need to be registered, in order to stop others using it, you can be flagged to HMRC this way too, so best to get your tax affairs sorted first, rather than get a huge back dated bill plus fine, and interest.