It isnt true that it stops at 18, if he's still independent and on a course that's not university level, he is legally entitled to cms support until even 20 (maybe 19, check).
Chase the arse off CMS, legally they have to act, bombard them they have set numbersbof days before they can and do take him to court, but wont automatically pass files across to the handlers to do this.
Also, I cannot see why he can't drive him there and collect him, I have rtt and can't see where you say his father can't do this and share fuel costs?
Its easy for nrp to pretend DC doesn't exist, need feeding, educating, clothing, housing, keeping warm, etc., just assumed that rp will pick up all slack (the one he calls cunt)
You know, the cunt that is there for the DC all the time and finances her DC to a tune far and above £40 per week!!
The cunt thats actually been raising the DC for 16 years, and can't just decide not to pay! Not to feed/clothe, etc.
Write to CMS, set out dates, amounts, and write again when you expect a reply that you've not had one, and then again when no money arrives, and again, then copy MP in.
Is there actually a reason he can't take him?