My ex-wife refuses to pay maintenance

My 16 year old daughter lives with me full time and never sees her mother and my 8 year old son lives with his mother Mon-Fri and lives with me Fri-Mon. My wife hasn’t paid CSA for my daughter in over 3 years however, she has only been unemployed for 1 year, March 2011-March 2012, and still refuses to either pay or pay the right amount. I pay for my son however, i don’t receive any payments for the 3 nights I have him or any benefits, therefore I am expected to care for 2 children with no help from their mother.

I have contacted the CSA on many occasions and have never been given any help. My ex wife also works 9-5, Mon-Fri and claims she only earns £8,000 per year, however I worked out that she’d then be working under NMW for Scotland which is illegal and when I informed the CSA about this they didn’t bother investigating. She can also afford to go on 3 holidays per year and buy a new car but I can barely afford to go for a day out with my children. It is also frustrating as my son wishes to live with me full time but the courts won’t listen to his wishes. Could you tell me what I should do next and how I should get my wife to pay for her daughter?