As a sole trader you adopt a "trading style" - the name your business is known as - but in all official references you are Ryan *** Trading Us "Widgets Are Us".

If you were to try trading as BP or ICI or Virgin Parts or whatever, I think you would have lawyers letters within 24 hours of them finding out. You could also find yourself open to charges of "passing off" or worse if you wre doing similar things to the "real" company.

If you go to www.companieshouse.gov.uk and click on Free Company Information there is a complete index of Limited Company names - no two can be the same, but if you fancied something like "Widgets Are Us Ltd" and if it is already in use, you MIGHT be allowed to register "Widgets Are Us (South) Ltd".

Going Ltd does incur higher legal and accounting costs, you have to file accounts annually, and pay for a tougher audit. Also, you end up paying double tax on any benefits you give yourself, like a car. First as the employer you have to pay the employers NI, then as the employee you pay BiK tax on the car and employee NI on the benefit.