Some interesting comments!
While the DDA requires "reasonable adjustment", if the premises are not capable of providing accomodation at ground or first floor, then how can the person be permitted to stay?
If staffing is not available 24/7, how would the person be evacuated? You can't provide a refuge and just leave them in it, they must be accompanied and have communications with the ground floor.
You could permit use of the lift on a one time only downward trip for the purpose of evacuation, subject to the risk assessment of course, but can the person get to it unaided?
If the reqiuest has come from the University to provide the accommodation, you could put the onus back on them to come up with some solutions ...... reasonable in my humble opinion!
I do know of a premises where a wheel chair user lives on the 5th floor ..... BUT .... their is a refuge almost immediately outside the flat door, the persons partner stays with them most nights (or a friend on others), when the fire alarm actuates, a friend calls the person on their mobile to check they are OK if it is known that they are alone .... and there is a PEEP in place which has been agreed with the person by the accomodation providers. There is an option to use the lift for an immediate evacuation if needs be, but this is a last resort.
The person in this case did not want to be separated from their friends and has accepted some risk, which is documented, along with the procedures for them.
It isn't impossible to provide the accommodation, it requires some very careful management and good friends!