Thanks A. This might be a long one then! 
We have been extremely lucky to have had an excellent primary that gave him absolutely everything he needed.
He has full-time 1-2-1 support - though currently easing off from this & working towards independence with just extra support in explaining the task and keeping him focussed. The work he produces is now entirely his own.
He uses a laptop for larger pieces of work.
He has "episodes of care" for: SALT (frequently), Physio (frequently for several needs), Occupational Therapy (rarely), Ed Psyc (as needed), Orthotics too - All of which the 1-2-1 manages and follows the programmes that they leave with her. (She really is incredible!)
He has a kind of distanced supervision at break times - to ensure he is not socially excluded, to watch in case he falls or bumps (hypersensitive & also hyposensitive), and to make sure he doesn't disappear off into some hidden corner & become lost or forgotten. This also watches for some remaining (though much improved) needs for assistance with dressing or personal care & dignity.
He also has an IEP which covers some social aspects of his development, e.g. circle of friends & small group work.
His intense interests are also catered for and managed well so that they do not over-ride his day.
He does manage to keep up with the curriculum though with some "reasonable adjustments" for his literal understanding and timing. His homework is also explained seperately and gone through to make sure he has understood what is expected and to cover his language differences.
So am wondering what of these are reasonable in a high school and what new situations / needs will also need thinking about?