You can trade as a business in the UK without a VAT number... But as Nigel said you'll need to send a Self tax report before the 31st of Jan each year on how much you have sold. The forms are daunting but do able.
I have a limited company.. I set it up with 100 Uk pounds and as a limited company, that is your liability.
But doing VAT every 3 months is a pain in the harris.. But you claim back against your sales. so life's a bit easier. And yes! I have an accountant, and he piggin good.