Refused change of shifts

I have worked for my employer for 10 years and have been on long term sick leave with stress/anxiety for months. I became a single parent last April and so was unable to work my usual shift pattern  as childcare does not really exist to cover them. They allowed me to work a better shift pattern on a temporary basis. The company did not follow their own policies and procedures when it came to the flexible working application I submitted and they exceeded the time limit on dealing with the whole matter as per ACAS guidelines. I raised a grievance over this which then went to appeal. They did not find in my favour. They were unable to provide any evidence to back up my concerns and I was fobbed off.  I have had 2 occupational health reports that both suggested that they implement the FWA to ease my anxiety and work-related stress. They have ignored the suggestions, stating that it did meet the needs of the business.  There is currently a single dad who works a family friendly pattern and has done for a number of years. I used this as an example of sex discrimination as part of the grievance, but their comeback was that the business had changed since they had implemented his pattern, but did not provide evidence to back this up.  My manager conducted a stress risk assessment which contained delicate information about my state of mind at that current time. He left this information on a desk which was in a place where anyone could have seen it. It was handed to me by a colleague a number of days after it was left there.  This was also raised in my grievance.  I do not believe it was ever investigated as a serious matter.  I recently attended a meeting regarding my sickness absence. As my circumstances have not changed and I am unable to return to work on their shift pattern they state they will have no alternative but to consider my dismissal on the grounds of inefficiency arising from my non-attendance at work. I have asked for an exit package.