hi there
ok ltd or trading as??
if ltd you need to register with companies house, and form limited company, you can do this online
you will need that info to open the ltd company bank account
and you need to register ltd for corporation tax, and paye
if trading as you need to inform HM Revenue and Customes of delf employment, partnership if applicable and paye if employing staff
hope that helps for a starters
regards
martin