Hi there. I would contact the University and find out if they have a disability department some even have a neurodiversity department. Some Universities offer subsidised accommodation if you can show that it is needed due to a disability and this includes autism. For example you can get an ensuite for the same cost as a standard room. Some will let you keep accommodation for the completion of the course.
You can also get extra time in exams which I'm sure you are already aware of and other adjustments such as using a computer, having a quieter space in hall for exams or even a completely different room. Some offer online 1:1 Mentoring and lots of other support which is really useful in the first year in particular when you are settling in. It's important to also find out about getting permission to speak on your son's behalf. There is usually some sort of form you need to complete for this but it's really useful if your son for example has difficulties with communication, making telephone calls to maintenance for example if something is wrong with room or any other difficulties. Hope this helps.
Edited to say: Don't forget about DSA (Disabled Student Allowance) which includes providing the support for 1:1 Mentoring