Ex stopped paying even though we had agreement

I have been seperated from my husband for 15 months we have 2 children together aged 3 and 7 both who attended ofsted registered child care. I claim tax credits for this. I agreed with my estranged husband to pay me £400 a month this included his half of a banckruptcy scheme that we are in. I have reciecved 3 months of this money but had nothing from him since dec 2011. He is self employment and keeps telling me he has had no work. I have his last 3 months bank statements but worry that any contact you try to make with him will be ignored as he will not answer his phone. It has got to the point where I am running out of people to borrow money from.

I have tried to discuss the situation with him but just keep getting told that he will have money next month.