That's completely wrong termabulan. You MUST register as self employed if you are trading as an individual or partnership. You have to inform the HMRC within three months.
Whether or not the OP has another paid job is compeltely irrelevant to the issue.
VAT will, as previously pointed out, not be a factor unless you are very quickly turning over a lot of money.
Potentially self employed National Insurance will be payable at �3 a week or whateer it is these days but if you are seriously playing at it then a de minimis limit applies and no NI is payable. You need to apply for exemption though.
You do not need to be a company to trade, you can do it in your own name or as a partnership but either way it will have to be properly registered and it fundamentally doesn't make a lot of difference which route you go down.