Just a thought Karina
PCS is big in the news here at the moment in relation to sports injuries (rugby & league in particular) - do you have any family, friends co-workers etc who have any connections to sports teams or clubs. They could maybe put you in touch with someone who could find out who the club uses as their consultant on this type of injury. I realize your son's cause of injury is different but the damage would be similar and should be within their range of expertise. Also if your son learns how common this injury is among sports players he might be a bit more accepting of his need for treatment.

Also the insurance co. not paying for the neuro/psych seems down-right mean penny pinching. Surely they paid for his initial emergency treatment and assessment (Xrays, MRI etc) for diagnosis - then they should obviously be covering this. I'm not sure if you have an insurance commissioner or ombudsman in Aust. but I'd threaten to take the matter to them if they refuse to meet their insurance contract obligations.
Hope this is of use - Keep fighting.