do you have younger children in the household?
the reason we were so confident that we would "win" if ex took it to court was that we have 2 younger children, on e of whom is disabled.
whilst dh is perfectly happy supporting his children through university (the level of maintenance they get means they are not required to take out student loans, although both have done so at the encouragement of their mother . probably in the hope that dh will clear them once they have graduated!), he was not happy with the thought that he was going to be paying a substantial amoutn to his ex, have her pass on less than half that amount to the dc and have them live on loans, and then expect him to top up the amount they were recieving too.
in his view, now that they are 18+, the money is theirs. he pays the same amount, but to them directly. since there is no obligation for parents to pay for university, I think any parent trying to bring a case on this would be laughed out of court.
there could be numerous reasons why dh didn't want to support his children at university, and indeed, many parents choose not to do so.
we figured that, since the same amount of money was being handed over each month, but cutting out the middle man, so to speak, she would not have a leg to stand on (especially if you figure in that dd1 causes us a lot of extra expense due to disability)