Ok OP-I had the same problem with a deadbeat dad who was also a "job-hopper", and I have dealt with the CSA for 14 years, and am now getting maintenance after very many complaints. My ex owed over 14 grand in arrears.
They can actually find someone's job in 6 weeks not 12,but you need to be pro-active.Find out who your case officer is,their direct number and call them weekly.If they forget about you,you go to the bottom of the pile.If you don't get anywhere, go and complain to your MP.You can e mail your MP, by looking on the Parliament website or contacting their constituency office. Keep a log of every letter,phone call,time you spoke to anyone and name of person, if you have to speak to the CSA. In fact complain to your MP anyway
I assume there is some kind of maintenance assessment in place.If there isn't complain till you get one.
If there is a maintenance assessment in place,find out what the arrears are.Get the CSA to get a liability order which takes your ex to court and enforces the debt.If they have already done this then they should be enforcing it.
If he moves job as soon as a Detachment of Earnings Order is in place, then get the Enforcement Team to credit check him and find out where is bank account is.They can apply for an order to take money straight from his bank in regular sums if he hops jobs (think this is fairly new).If it has been to court for enforcement action and a liability order, the CSA can apply for a 3rd party Debt Order to take a lump sum from his bank.
They can also apply for a case officer to go to his home.They did this with my ex, and that spurned him into reaching an agreement with me,which worked for a while,but he stopped paying AGAIN, so back to CSA I went.
Baillifs are not always the best,but sometimes the shock of having baillifs turning up on his doorstep may scare him. They can use this to enforce as well. I did get some cash via baillifs :)
For anyone who is self employed, the CSA have the right to walk into any business and check the books,they don't often use it.
My kids are adults now, and I am still chasing arrears, and (fingers crossed) , I am getting them at the moment.
All I can say to anyone chasing maintenance is complain LOTS,hassle them weekly LOTS, if you get a payment and it has to be received by a certain date,make sure you phone the CSA to check payments have been received as employer is supposed to tell CSA within a few days that person is no longer working for them.Make CSA call employer for any none received payments etc etc.
Any more advice I can give in my 14 years experience of dealing with this eejit bunch,just ask.Actually present case officer I have got is great, probably cos he doesn't dare cross me :)