ivyk - Yes, sadly I am sure. The 1991 Child Support Act that created the CSA also took away an unmarried parent's right to pursue the NRP for maintainance through the courts; it is only possible to make a private arrangement or go through the CSA :(
(Here are a couple of sources for anyone who's interested: a and b )
Choc - Yes, initially it was entirely down to the incompetence of the CSA. When they had failed to take any action - and had not even made an assessment so he was not actually liable to pay anything and I had therefore lost thousands - they acknowledged their fault and paid me maximum compensation. However, this was a paltry £400, which represented around 10% of what I had lost. Yes, I contacted my MP; but there was nothing more they could do, since I had already had maximum compensation.
After this, the CSA made an assessment and began to take some action, but slowly and incompetently. It became clear that DS's father had no intention to pay anyway. He left two jobs at the point the CSA contacted his employer. Finally, around 10 years after I had first contacted the CSA, he left the UK to work abroad in a country where there is no 'reciprocal arrangement' so he cannot be pursued there. He has now been there for about 4 years. All in all, it is about 14-15 years since I first made a claim for maintenance, and I have not received a single penny.
Last time I checked, he owed around £25K in assessed arrears, but that was a few years ago. Tbh I stopped asking, because I found it so incredibly frustrating to be told again and again that he had paid nothing and there was nothing I could do. :( 
We have done OK. We (well, I!) 'cut our cloth according to our means' and we live modestly but quite comfortably. I work and I own my own house. I am proud to support my children by myself... But as DS1 has started to talk about perhaps going to university, I have started to think about the fact that I will not be able to help him out much, and that that £25K we haven't had - and will probably never get - would have gone a long way towards paying his fees... :(
The CSA is not fit for purpose. Frankly, given the appalling way in which so many families have been let down, I think someone's head should roll. But whoever is in charge will probably get a knighthood instead. 