Doctors private letter used to deny Access

Access

Hi all, I have posted on here fairly recently regarding being denied access to carry out EICR and CP12 checks and inspections by tenants who have claimed to be Extremly Clinically Vulnerable.
After much deliberation they had agreed, or it appeared they had agreed for an inspection and the CP12 to be carried out on the 6th July. Wrong, although they are close to the end of a section 21, (mid September) we still need these checks carried out for insurance purposes, that was the subject of our initial posting and we assumed everything was on course for the 6th.
It appears that they intend to leave before a court order is sought, but have missed this months rent.
To make things more complicated they have sent our agent a letter from her doctor anouncing that because of the health conditions of one of the tenants, the doctor is actually suggesting that we should leave these inspections till after they have left!!!
A couple of things spring to mind here, if we are meant to leave things go, as the doctor suggests, what happens to the keys, what happens to the vacate report and inspection, what happens to any rent owed?
We have many questions but these are just a few.
Is it possible for us to use there deposit for owed rent? it is protected by the DPS. (Avoid the DPS0 at all costs)
Any help would be appreciated, and thank you in advance.