How can we get the money that he owes us?

I have a daughter who is 17 and in full time education. Up until 6 months ago my ex was paying me 20pnd a week 4 her.

We recently asked him 4 the money he owes but he said he is skint, he has a full time job and can afford to goto football and on holiday etc but says he cant afford to give me 20pnd a week. he and his wife both have full time jobs.

I am the only 1 who works in my house as my husband is disabled.

Is there anything we can do to help us get the money he owes?