We are in the same position, 16-18 is a black hole for so many things if your dc has SEND or incapacitating illness.
My 16 year old ds has been too ill for school for a couple of years. He was still on roll and being tutored at home by the LA until lockdown, but entitlement to home tutoring ends at 16, unless an EHCP is in place. Of course our LA spent the whole of last year fighting us and refusing to assess, so now he’s NEET, while we continue the fight.
I only twigged re prescriptions when his needed renewing, as he has always 3 month’s worth delivered via a service from a children’s hospital, which of course is also no longer the case, as he has been moved to adult care.
You also lose child benefit for them, as they are no longer in full-time education.
Basically , if your child is medically unable to attend an educational setting full-time, post 16 they disappear and are no-longer anyone’s priority. LA’s are supposed to have a NEET team to follow up and help these cases in relation to education but, in reality, we had one emailed form to fill in and as he is too unwell to physically attend education, they just say ‘let us know when he’s better’ (which he won’t be) and leave it at that.
Other teens in the same situation, due to the same conditions as my son, are routinely refused PIP and don’t get anywhere without a monumental battle, involving tribunals. If we do that we will have to simultaneously go to tribunal for that and his education, whilst already caring for a sick teen 24/7. (Apparently they don’t need PIP, as their parents can care for them, because they are still children, yet for everything else they are considered adults and qualify for nothing if they are not in full-time education, which the LA refuse to provide because the are now over 16 - and round we go!) Everyone tells you to apply for PIP, but none of them realise what a massive fight that is, especially when you are already dealing with so much.
It’s an absolute disgrace, but no-one is interested.