Statutory Demand What next?

Rent Arrears

I have issued a Statutory demand on 03/06/13 to two student tenants who are both over £1000 in arrears. They do not appear to be overly concerned and keep assuring me they will pay the rent arrears. However their tenancy is due to end in less than a week on 30/06/13. If I proced to Bankruptcy I am not sure how I go about this and I have resad on the internet that if someone is declared bankrupt the debt is wiped away and that it is quite possible to be clear of bankruptcy in 6 months. Can you advise me of my options please? Do I need to act now in any way? I have not heard that they are contesting the demand in any way or doing anything at all. Thank you