You can see why fishy said this, Spud!
You don't know for sure that your ex's earning all that he says. It could be for bravado, or to somehow make your daughter feel that her daddy's not a loser.
I'm sure the CSA, for all its faults, know what's what, and unless your daughter attends a private school and so on, the �175 a month wasn't bad to begin with - IF the �115 a week was right.
Bear in mind you could've found another partner who might be supporting you as well, in which case the �175 a month would've been a bonus, yet left your ex with virtually nothing. Sorry, I don't know the details, but sometimes in these cases, the men come out worst. If it's true that your ex earns more than he says, then get the proof and show the CSA. Whoever employs him should have to tell them, so maybe he's exaggerating to you?