DLA to PIP

IS there any advise on asking for a continued paper assessment rather than a home visit. Initially sent apt for assessment at a centre despite saying on initial form that this would not be possible for my husband and 'respectfully' asking for home assessment. They accepted this and sent home apt.
This however stressed my husband so much he had a psychotic episode which built up over a couple of weeks and he had to be taken in to hosp. and was sectioned.
This has never happened before and it was felt that the worry of the interview was a main factor. The hosp. requested a 'paper assessment' on his behalf which was initiated.
He was discharged after 2 weeks and immediately I was told they would revert to a home visit. I explained the situation (I have to deal with it all because my husband cannot cope with it).They agreed to continue with the paper assessment at that stage but because the GP did not fill in the form with enough information about 'how his illness affects him on a day to day basis' (they can't, the GP who filled it in didn't know him but happened to be on duty the day he was admitted and got involved with that situation), we have now been sent another apt for a home visit.
Have sent two 'begging' letters since with info also from the hospital notes because I am so worried that it could happen again. What is there to stop it as his physical and emotional problems remain the same. Can't tell you how many phone calls I have made and paperwork I have sent to them, all by registered/special mail because my husband can't bear the thought of personal details/problems going through the normal post.
Is there any advise you can give me please. Thank you. Mrs P.