Get in contact with university Disability services and also apply for DSA on student finance website. You can have a virtual meeting with a disability advisor from the University before you go and sort out a learning support plan with detailed support for accommodations and also so if needed they give you a mentor to talk to every week. A specialist mentor one for university/study issues and another one for mental health and non-related academic stuff - ask for this. They can also refer you to university mental health therapy services.
I'd also recommend changing GPs (pre register so let a new uni GP know you're coming and let them know all your details and issues in advance), and then ask your home GP to prescirbe a 1 month supply of any meds just before you go so you don't run out. If your dc isn't on meds, see about getting on them for stability reasons and the stress of moving to a new city with uni at the same time . Also ask about moving any therapy to be accessible near the university or whether the university GP should refer you somewhere else (whatever systems they have the GP will know specifics)
Search up X uni Disability Sevices most unis have a page with links for how to registers, detailing all the support and processes, key emails of staff, and forms to do etc. Just a page signposting you to everything which will likely be helpful to make sure everything is done in advance. Your dc needs to have a meeting with one of the universities' Disabilities Advisors first to make a new LSP - if there's a website page with all the details, I'd look on there first to email them and ask. You should join the meeting/assesment with the Disability Advisor, if you don't think your dc will go depth on his issues.
Disabiltiy Services are very good with this adding exam arrangements (extra time, rest breaks, scribe, separate room - ask for all the possible exam arrangements, as universities have lower thresholds), tools so recording lectures, and your dc should also have get some assistive technology from DSA which can help.
In the meeting with the uni disability advisor (separate from DSA) they can go through everything the uni can offer including telling all lecture staff (as they change about him in advance). Then then can create after it a Leanring Support Plan (share it with all staff, who come in contact with him, including personal tutor and lecutre staff as they change). They will send him the copy of the LSP before they approve it asking if the wants anything changed etc ( so check for those emails).
Your DC needs to go to office hours, and have sessions with his personal tutor (should be subject specific). Talk to his lectures, his Disability Advisor regularly, his DLO. For most of these he needs to reach out first and then they will offer more support. DLOs are Disability Liason Officer - they tend to be lectures and people in the school your dc is studying in (so school of history and philosophy, school of geography). You contact them for info on extensions, exam issues etc and Disability Advisor for more general things (this is their whole job unlike DLOs who are often teaching staff).
During the DSA Needs Assessment, at the end they ask you if you want to consent to it being sent to the univeristy (normally in advance of you starting) so they know what support they are recommending your uni disability service implement (academic mentor 1-1, mental health services etc) and then the student doesn't have to chase all of it themselves. Make sure you say yes to this.