oh no essbee (not sleeping before 12- for me that makes all the difference- much sympathy coming your way as I hate it when he's up until that time).
I think if you could get a social worker it might make all the difference. A warning though I have found dealing wiith SS incredibly frustrating and a stress in itself. if you are feeling low it might be an idea to get someone to help you with this.
I don't think that HV have official input in children of 7, supposedly they have been transferred to the school nurse system. There are huge staff shortages of school nurses but you should be able to request and appointment. Would be worth doing as what you need is someone to help you access the supprot your son needs. If you have a gen of a nurse she may help a lot.
Thinking of you. Do you have access to a paediatrician? If your son is often up late it might be worth asking about melatonin.