The CSA are a waste of space and totally incompetent. I have a huge family and various nieces & nephews have been involved with the CSA and a couple have been driven to the brink of suicide.
One niece separated from her hubby in Jan 2007 and got the CSA involved. Her ex has paid �350 a month to the CSA and my niece has never received a penny. She's seen her ex's bank statements showing the money has been paid but the CSA has "lost" it and can't find it.
Another niece has been divorced for 3 years. Her ex has been in the same job for 15 years so you would think it would be simple for them to take the money from his wages. Wrong. She too has never received a penny. The CSA can't be bothered. Every 3 months or so the CSA send her a cheque for �50 for compensation for their incompetence.
Given you ex's circumstances, you don't stand a cat in hells chance of the CSA doing anything for you.
All I can suggest is you try and gather as much info and evidence as you can regarding your ex's work and then grass him up to the Inland Revenue.
You won't be any better off financially but I bet you'll feel better!