If you are a UK national living here there's no need to register anything. Call yourself what you like. For example: "David Green Trading as FatCure".

It's convenient if you open a business bank account in that name. In this way you can accept and make cheques in the name of "FatCure".

When you start to make a profit, tell your local tax office.

That's it!

VAT Registration

You don't need to register for VAT until your turnover approaches the monthly equivalent of around 61,000 GBP per annum (check this as it keeps changing).