Hi e_m, yes it can be annulled for 2 reasons. If you were proven to have wrongfully been made bankrupt by a creditor. Or if you should acquire sufficient funds to pay off all your debts in full, plus the OR's fees plus the trustee's fees.
In addition to the two that John mentioned, you can also enter a post bankruptcy IVA if you have sufficient income or assets to make an offer to creditors.