Hi, I am planning to create a small webdesign company (become a sole trader, not sure I can call it a company

). Since I am from EU, I don't know much about it, and started to research the topic just yesterday. The questions I want to ask are:
1. I know I can't register a name on Companies House when I am a sole trader, but can I use a name of my choice, eg. XYZ Webdisign (assuming there is no such company), or do I have to use my name, eg. Mark's Webdesign Services? I don't really care if someone steals the name from me, because I don't expect the yearly income to exceed £3000.
2. Do I need to have a business bank account, or can I use my personal current account (I will be also employed full or part-time)? I'm asking this, because I might need an auditor's certificate of balance, and I am not sure how will that work when the income from employment is mixed with income from my business.
3. Am I correct that I won't have to pay anything for my business apart from taxes? Since I will have an income of £3000 at most, I will not have to pay NI (Small Earnings Exception), and not have to pay VAT either. Will the fact that I will be employed somewhere else affect any taxes?
4. Can my business get cancelled, eg. if I don't have any income? I don't mean the bankrupcy, I mean the situation that I don't have any customers - my costs will be neglible.