If no response is received from the debtor to the Winding up Petition the Court usually orders that the debtor be wound up at the hearing, as long as all the required formalities have been complied with and a liquidator is then appointed.
If you wish to formally liquidate the company at the final hearing stage, then you would need to pay a further £1550 + VAT being the balance of the Official Receivers Fees however this is entirely optional.