The organisations MIND and SANE are very helpful. Both have websites, Also, I know MIND has a legal advice department. A good mental health Solicitor may be helpful in explaining his rights as a patient, ensuring he receives proper treatment and care, etc.
Also, where money is concerned, your local council should be able to assist with In/Direct Payments. or Independent Living Allowance, for some expenses, but it may be best if you handle the bookkeeping for this as councils are strict as to the expenditure of this by patients and/or their carers.
Wish I had know this a few years ago.
Hope it all goes as well as possible for you and your son.