Hello David and welcome to the forum.
A winding up petition can have some vary serious effects on a company. If the petition is granted by the court, then the company bank account will be frozen and trading suspended pending a winding up hearing. If the court decides that the company should be closed, then a winding up order will be issued.
For more information about winding up, have a look at:
http://www.company-debt.co.uk/winding-up.html