You might disagree with me Petal02 but you are still wrong (and, I suspect, you are not a lawyer?). The advice you received may have been the correct advice in your circumstances but it is well established that a child over the age of 18 can sue a parent for maintenance through university. If there was a maintenance order in place before the child reached 18, then the means by which the adult child may apply for maintenance on her own account is to issue in the old divorce proceedings between her parents. Provided both parents are still alive (as in the case of your DH), this is possible. Alternatively, the mother/NRP can issue on behalf of the adult child under Schedule 1 Children Act 1989.
I recently read a thoughtful account of the development of the law in this area, which you might find interesting: Maintenance for adult children.
If you are really interested I'd also suggest you look at the 1976 case of Downing v Downing (Downing intervening) ([1976] Fam. 288), which established that the court absolutely has jurisdiction to hear an application by an adult child for maintenance through university. This was a case where BOTH the parents of the unfortunate child refused to maintain her at university. The following excerpt from the judgment is relevant:
'It is perhaps worthy of mention that an application of this kind would not be a unique instance of a child over 18 taking proceedings against its parents for maintenance. Where a maintenance order has been made under section 23 of the Matrimonial Causes Act 1973 for payment to children and the father falls into arrears, the mother cannot herself take out a judgment summons to enforce the arrears because she is not the payee. If the children are minors, the wife or some other approved person will issue the judgment summons on the children's behalf as next friend, but, if the children are of full age, it would appear necessary for them to bring their own enforcement proceedings. This is the opinion of the editors of Rayden on Divorce, 12th ed. (1974), vol. 1, p. 884, with which I agree. Under section 12 (2) of the Guardianship of Minors Act 1971, where a person who has ceased to be a minor but has not attained the age of 21 has while a minor been the subject of an order for the payment of maintenance, he as well as the parent may apply to the court and the child may ask for an order requiring one or both of the parents to pay maintenance to the child himself. The provisions of section 12 replace section 4 (1) and (3) of the Family Law Reform Act 1969, and by section 6 of the Act of 1969 identical provisions are made in favour of wards of court, who may also in similar circumstances apply for orders against one or both of their parents.'
Some of the statutory provisions referred to in that excerpt have since been repealed, though they are replicated in codified statute that is now in force.
Advice which may have applied to your case is not one-size-fits-all.