So if insurance is valid for business use, then there are no other legal require before using the van commercially? What about tax etc?
No other requirements. Car tax and everything is the same.
In terms of personal tax you can claim 45p a mile against your tax as a business expense.
Can I clarify anything else?
I am already registered self employed as a sole trader (language trainer and consultant) . To use the van would I need to register again as a sole trader in a separate business? Or can all my sources of income be declared together?